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Chapter Text

After Mr O’Neil had been brought to his home (and the turtles had left April to explain everything to the still-confused and recently de-mutated man), the brothers had called the night a mostly-success and had headed to their own home.

“Dudes” said Mikey around a yawn, “I am so tired. It’s not easy being Turflytle all night. Buzz buzz” he ended halfheartedly.

It was a credit to how tired Raph was too that he didn’t even attempt to retaliate to “Turflytle’s” annoying buzzing. All of the turtles seemed exhausted from the long night of battling Foot bots and apparently now mutated Baxter Stockman. All of the turtles except for Donnie, whose face was stretched in a wide grin as he practically bounced around the Lair.

“Retro-mutagen!” he exclaimed, elated, “I actually managed to create working retro-mutagen! I cured Mr O’Neil!”

“We know, Donnie,” snapped Raph tiredly from where he had collapsed into the beanbag in the pit, “We were there”.

Raph’s biting comment did little to dent Donnie’s excitement, and he kept his beaming smile as he practically dashed towards his lab. Leo watched the scene with a proud smile for all his little brother had accomplished, and at how much joy it brought him. There were few greater things that an older brother could wish for their younger siblings. All the same, he knew that Donnie must have been as exhausted from everything as the rest of them.

“Look, I know this was a big night, but I think we should all try and get some sleep” the leader suggested with a particular glance shot at the thrilled scientist.

“I agree with Leo” added Mikey with a tired raised hand from where he had laid face-down on the floor.

“Sleep? Now? Are you kidding?” gasped Donnie, “This is the scientific breakthrough of a lifetime, it could be my greatest accomplishment! I can’t sleep , I need to record everything about the retro-mutagen! I could--” his sentence cut off, and for the first time in the night his excitement seemed to dim as he got a thoughtful and distant look in his eyes, “I could even start making more retro-mutagen”. His gaze drifted to the open doors of his lab, and his distant expression turned somber.

“Timothy” he said softly, as the full weight of what his discovery could mean finally hit him, more than just the thrill of making something new or solving a difficult chemical problem. He realized that with the retro-mutagen, he could finally make up for his biggest mistake, his biggest failure. He could keep the promise he had made.

He resumed his dash into his lab, but this time was fueled by determination rather than excitement. His brothers watched, wondering whether they should follow him or just go to bed. Sighing, Raph, ever the protective brother, reluctantly got up from his place on the beanbag and followed Donnie into his lab. Leo followed seconds after, and Mikey tagged along right behind him.

They all found Donnie standing in front of the container that held his once-human protégé, his hand placed on the ever-cool glass as he stared into the mutant’s still-fierce expression. It had been months, and his frozen form still showed no signs of thawing. Surprisingly gentle, Mikey pulled his taller brother into a side-armed hug, as Raph and Leo stood comfortingly close by.

“It’s ok, D” he said reassuringly while holding Donnie a little closer, with utmost confidence in his genius brother, “You can cure him now, it’s all gonna be fine!”

Slowly, Donnie brought his own arm around his only little brother’s shell, responding just as slowly and thoughtfully, “You’re right, Mikey. I can”

“In fact,” he added, finally tearing his gaze away from the ex-human, to glare determinedly around the room, “Now I can help anyone who has been mutated by the Kraang. All those people who were affected by mutagen, who maybe even lost their minds to it like Mr O’Neil or Timothy. We can help all of them! I mean, you said there was a list, right, Leo?” He turned to Leo, his eyes silently asking him to agree, to help him with this mission.

“You bet Donnie”, the leader in blue responded without hesitation, “Spilling that mutagen all over the city is still our mess, and we still have to clean it up. And now we don’t have to just grab the canisters of mutagen before they hurt people, we can actually help those affected”.

Raph spoke up, interrupting what was sure to turn into a dramatically heroic Leo-speech fueled by fatigue, “Um, hate to sound like a jerk--”

“Since when has that ever bothered you?” quipped Mikey effortlessly.

Raph didn’t justify the comment with a response, and instead barrelled on with his own comment, “But don’t most of the guys that mutated want to kill us ? Why should we help them?”

“Most of the ones that want to kill us want to kill us because it’s our fault they got mutated in the first place” countered Donnie, with another glance towards where the Pulverizer sat frozen with a vicious expression. “It’s the right thing to do, Raph”.

“And anyway” added Leo, slightly annoyed that his big speech had been cut short, “Wouldn’t you rather deal with a human trying to kill you than a mutant?”

Raph blinked, processing the idea. “Yeah,” he replied after a moment of thought, “I can’t argue with that”.

“Alright, boys!” cried Mikey, releasing Donnie from the hug to jump up onto the counter, posed heroically. “Time to cure the world! We should totally come up with a cool name! Like, Mutant Busters! Or The Cure Squad! Or, Or--!”

“Yeah!” cried Donnie, just as pumped, but showing it less enthusiastically then the energetic younger turtle, “We’ll cure them all! Innnn about three months”. The brothers all turned to stare at Donnie, who now seemed to be radiating faux excitement, probably trying to keep morale up. At their questioning stares, he cleared his throat and clarified. “Retro-mutagen takes months to properly synthesize. Plus I need to track down more mutagen in order to make it. But don’t worry, now that I know what to do to make it it should only take about” he ran some quick calculations, “Two months and fifteen days instead of the nearly five months it took the first time”:

“Duuuude” complained Mikey, his posture deflating with disappointment, “You got me all hyped to be a Mutant Cure Squad! Now I gotta wait two months?!”

“I mean, seriously” also complained Raph, “Can’t you make it any quicker? Your and Leo’s lame speeches actually got me all pumped, and now I have to wait? What are we supposed to do for two months?”

“Well,” suggested Donnie, “We do still have to collect all of the remaining mutagen canisters. Plus we need to find the mutants to cure them. I mean, we haven’t seen most of these guys since we first met them”.

“That’s true” added Leo, starting to count on his fingers, “Spiderbytez, the Squirrelinoids, Dr Rockwell, Snakeweed. Who knows where those guys are!”

“Man,” commented Mikey offhandedly, “We sure mutated a lot of people”.

“Ok, fine” growled Raph, “We’ll keep looking for mutagen canisters.Then, in two months--”

“And fifteen days” interjected Donnie.

Huffing, Raph continued, “In two months and fifteen days we take the retro-mutagen with us and we de-mutate them all”.

“Alright!” cried Mikey, flipping off of the counter and back to the ground, “The Mutagen Cure Squad is a-go!”

Two Months (and fifteen days) Later…

“Guys!” shouted Donnie from inside of his lab, “I finally got it!”

Everyone immediately halted in their activities, and ran towards Donnie’s lab, where he was proudly holding up a half-filled beaker of red-orange ooze of retro-mutagen.

“Wooooww” admired Mikey, “I mean, I know you made this before, but now it’s even cooler because I know what it does!”

“That’s all there is?” questioned Raph, eye ridge raised skeptically.

Glancing down at the half-filled container, Donnie shrugged, and replied, “Well, yeah. But it only takes a drop to work, we learned that from Mr O’Neil. This should be more than enough, as long as we use it sparingly” he stressed with a special glare shot at the youngest brother, who had leaned over the counter to look at the retro-mutagen more closely. Mikey laughed guiltily, and immediately backed away from the counter.

“So,um, Donnie,” said Leo hopefully, “Does this mean you can help the Pulverizer now?”

Unexpectedly, Donnie, instead of looking excited or hopeful, glanced aside and sighed. “I wish I could, but unfortunately, “ he gestured widely at the frozen mutant behind them, “Timothy is still frozen solid. I can’t know how that would affect his de-mutation. It could kill him for all I know! Before I cure him of his mutation, I need to find a way to thaw him out”.

“Oh,” responded Leo, shifting awkwardly before laying a comforting hand on his purple-banded brother’s shoulder. “Well, that can’t be as hard as making a retro-mutagen, right?”

“Yeah, D” added Mikey cheerily, throwing his arm around Donnie’s shell, “If anyone can figure it out, you can!”

“Indeed, my son,” the turtles all jumped slightly at the sudden presence of their father. “With your knowledge, I am sure you will be able to keep your promise”.

Donnie smiled shyly at the praise. Though Splinter was far from a cruel father, praise was something he gave only when he felt it was truly deserved. “Thanks Sensei”.

“In the meantime,” he addressed to all of them in a more serious tone, “there are many other mutants that still need to be cured”.

“Sensei is right” added Leo, arms now crossed over his plastron in attempt to look more serious, “We need to start tracking them all down to de-mutate them”.

“So where do we start?” asked Raph, his sai clenched in his fist.

“I seem to remember a group of dangerous squirrels attacking our home,” suggested Splinter with a slight tone of chastisement, “Perhaps it is time you took care of that problem”.  

Leo laughed nervously, before replying, “Hai, Sensei”.

Nodding in approval, Splinter laid a reassuring hand on Donnie’s shoulder, saying, “You have done a great thing, my son. Now ” he continued, releasing his genius son’s shoulder and once again turning to all of his sons, “Go help the other mutants”. The turtles bowed in agreement, and with that, the Sensei turned and left the room, leaving the team to plan their mission.

Straightening once Splinter had left the room, the teens all turned to each other.

“Well, you guys heard Sensei. We’re going on another squirrel hunt,” said Leo in an authoritative voice.

“Um, excuse me, Squirrelinoids,” corrected Mikey, “Also, uggghhhh,” he cried, “We have to try to find the Squirrelinoids?! I hate those things!”   

“Suck it up, Mikey”, grunted Raph, rolling his eyes.

“Alright,” said Donnie, already bustling around his lab to prepare for their mission, looking from shelf to shelf, “I think I can find a good way to distribute the retro-mutagen. But first things first,” he paused in his searching to look at his brothers seriously,  “I need to to lay some ground rules”. His brothers, except for Leo, quietly groaned.

“This is important, guys,” he stressed, “Okay, rule one, and this is the most important rule, be very careful with the retro-mutagen. DO NOT let it touch you. I’m working on making us all special gloves to minimize our risk of exposure. If we come into physical contact with this it would essentially kill us , removing the mutations that give us sentience and turning us into normal turtles. Do you all understand?” Donnie stared them all down fiercefully, even his older brothers, even the leader of the team. They were all slightly taken aback by the commanding attitude Donnie had. But they all nodded in understanding.

Donnie seemed to deflate with relief, glad that he had conveyed the seriousness of the first rule. He continued, in a more normal lecturing tone that immediately set his brothers at ease with its familiarity, “Ok, rule number two, while less imperative than the first, is still important to keep in mind. This” he gestured to the beaker of red-orange ooze, “is all the retro-mutagen we have for now. As you know, it takes a while to make more, plus, you know, I’d need April’s blood to make it,  so use it sparingly. Additionally, it only takes a drop to properly cure something, so don’t go crazy with it unnecessarily”.

“Third, and I don’t think you guys will like me for this, as long as the mutant is sentient, it should ultimately be their choice whether they want to be cured or not”.

“What?! Donnie, you can’t be serious!” yelled Raph, “Do you even realize how many of those dangerous freaks want to kill us? And you want to let them?!”

“I kind of agree with Raph on this one,” added Leo reluctantly, “It seems like it would be more sensible to change the more dangerous mutants human, whether they want it or not”.

Shaken, but still holding firm to his ideals, Donnie shook his head and explained, “It’s just not right though, Leo. We’re trying to use this cure to help people. If the mutant is fully cognizant and consciously prefers to be a mutant, who are we to say they can’t?” Donnie took a deep breath, reminding himself of why he decided to set this rule, and reassuring himself that it was the right thing to do.

“That’s the rule, and I’m sticking to it. At any rate,” he added in a lighter tone, “it’s highly unlikely that any of the mutants that were originally humans would even want to stay as mutants. And any of the sentient ones that used to be animals we can’t ‘cure’ for obvious ethical reasons”.

Raph scoffed fondly at his idealistic younger brother, “Donnie, you’re such a moralizer. But, I guess you are right. Even if he’s dangerous, I don’t know how good I would feel about turning Spike back into an ordinary turtle”.

“So are those all of the rules?” asked Leo.

“Um” replied Donnie, counting on his fingers and going back over the rules, “Yeah, I guess that’s it”.

“Whew” sighed Mikey in relief, “Only three rules. I think I can handle remembering that”.

“I hope so,” said Leo, “because we’re going after those Squirrelinoids as soon as Donnie gets the retro-mutagen ready. It’s about time we got those dangerous creatures out of the sewers, and stop them from hurting anyone for good”.

“Mutant Cure Squad is a-go! Again!” cried Mikey enthusiastically.

Chapter Text

Chapter 2: Squirrelinoids

“Remind me again why the squirrelinoids were our pick for first mutant to go after?” grumbled Raph from his place at the back of the pack as the turtles searched deeper and deeper through the dark sewer tunnels.

“Because” replied Leo while scanning the dark for any signs of mutant activity, “they’re a potential danger to civilians, and we’ve put off this problem for long enough. Also Splinter told us to.”

“Yeah, Raph,” inputted Donnie, briefly looking up from the mutagen scanner to fiddle with the syringe he had partially filled with retro-mutagen, “Did you expect flushing them down the sewers to magically solve the problem? It’s not like they drowned or anything. They’re probably still wandering around somewhere”.

“What?!” exclaimed Mikey, “You’re telling me my genius plan didn’t actually work? But it worked in my comic!”

“Yeah, but in your comic the aliens were flushed into space ,”  sighed Donnie, “where there’s no oxygen ? The sewers wouldn’t exactly kill them, just...hold them for a little while”.

Mikey silently pouted as they turned down another tunnel, following Donnie’s lead as his scanner searched for any trace of the rogue mutants. The dank tunnels were quiet except for the beeping of the mutagen scanner, and the distant trickle of water. It seemed like nothing could live down in the man-made depths, let alone monster squirrels, until the illusion was shattered by the occasional darting rat brushing against their feet. They had been wandering down here going further and further from the surface for nearly two hours, and so far the search had been a bust.

“I’m just saying” continued Raph, breaking the heavy silence of the lifeless underground, “Couldn’t we have chosen a mutant that was less dangerous? Or that was above ground? Or that wasn’t a crazy murdering monster that could suddenly attack us out of the dark and we would have like no room to defend ourselves?”

“Raphael” teased Leo, glancing back from where he stood just behind Donnie to smirk at his younger brother, “Are you telling me that you’re scared?”

“I’m not scared! Who said I was scared? These are totally rational, not-at-all fear-fuelled questions”, Raph vehemently denied.

“It’s alright, dude” comforted Mikey, “I’d be scared of mutant monsters that had replicated inside of my stomach, too”.

Fortunately for Raph, the darkness hid his sickened expression, and how his face turned a little more green than usual, “Not helping, Mikey!”

“Guys, stop it” snapped Donnie, briefly looking up from his scanner to pin his brothers with a criticizing glare, “I can barely hear my scanner with all of your arguing!”

“Who cares?” complained Raph, glad to be off the subject of his supposed fears, “Even with you being able to hear it, we’ve been at this for two hours for squat! We haven’t found anything!”

Donnie opened his mouth to reply, but was interrupted as the beeps on the scanner grew quicker and more frequent.

“Looks like the hunt is on” he said instead, continuing on in the direction of the beeping scanner.

“And it wasn’t on before because….why?” grumbled Raph, both still scared and glad to finally be able to deal with fear the way he knew best: punching it.

Ignoring Raph (which had become the norm in the last half hour), Leo turned to everyone and tried to turn the mood more serious. “Ok, everyone, here’s the plan (since it has been like forever since I last said it),” Donnie couldn’t help glaring at the subtle jab, “Donnie has the retro-mutagen, so me, Raph, and Mikey will try to incapacitate the Squirellinoids, and then Donnie will spritz them with some of the retro-mutagen. Everyone needs to be extremely careful while that happens, unless you want to spend the rest of your life being fed pellets in an aquarium. On that note, everyone got their gloves?”

“Yes, sir” replied Raph in a mocking salute, “For all the good that will do.”

“I’m still working on something more protective, but for now it’s better that you have the gloves than nothing” said Donnie, as the team pulled on pairs of specially made for mutant turtle hands, elbow-length gloves. Mikey couldn’t help but giggle at the comically-large length of them. “They look like something from some super-cheesy sci-fi show”.

Leo continued, “Alright. Raph, got your rope?”

“Yup,” he replied, twirling the hooked end of his grappling line.

“Mikey, do you have your kusarigama?”

“C’mon Leo, I’m not that dumb. Of course I’ve got’em!”

The group stopped as the tunnel they were in reached a larger chamber, and the beeps became so frequent that one could hardly be distinguished from the other. All at once, their posture straightened, and they looked less like a disorganized group of teenage brothers, and more like a skilled and deadly team of ninja. Donnie quickly turned off the scanner and tucked it in his belt. Sending a quick nod towards the rest of the team, he slipped into step behind them, and they all silently moved into the chamber.

The three mutated squirrels were restlessly sleeping in the center, curled up on a mess of garbage of chip bags, shopping bags, ripped up cloth of unknown origin, and various bodies of small birds and cats. Their dinners. Mikey stifled a small gasp at the sight of the mutant nest.

With a quick glance around the room, Leo confirmed that all three of the squirrelanoids were there, and signaled to the incapacitating-team. Each brother flanked out to take down a mutant-squirrel each. Leo counted down on his fingers, and at zero all three of the teens quickly and stealthily threw ropes or chains around the napping mutants. Instantly, the killer squirrels shot awake, and thrashed in attempts to throw off the binds. Leo, Raph, and Mikey held tough, wrapping the chains around their wrists for better grip, and leaning against the squirrelinoids with all of their strength.

“Any time now, Donnie!” shouted Raph as he tugged the fighting squirrel mutant back.

Not wasting time or breath on a response, Donnie pulled off the safety cap of the retromutagen, and dashed towards the one Mikey held, the most likely one to break free first. Taking an extra careful second to aim, so as not to accidentally hit his younger brother, Donnie spritzed the struggling mutant before immediately moving on to the next one. One after another the raging rodents were sprayed with the cure for their monstrous mutations, and they all struggled harder, but as their elongated limbs shrunk back into place and their fur grew back in patches, the squirrels gradually calmed down. After a brief moment, all of the brothers let out a relieved breath as the sewer tunnel was left with nothing more dangerous than three scampering, normal squirrels.

“Aw, yeah, boi!” cried Mikey in victory, sharing a cheerful high-three with each of his brothers, “The Mutant Cure-Squad was a success! Let’s get pizza to celebrate!”

“Just let me do one thing first” said Donnie, carefully approaching the wandering critters with a cat carrier in his hand. He quickly herded the still somewhat disoriented squirrels into the carrier, and then turned back to his brothers. “Ok, now we can go”.

The brothers headed up to the surface to get some Antonio's, joking and playfully shoving each other, but Donnie hung back a bit. Pausing for a moment, he opened up the carrier and nudged the squirrels out. The normal, harmless, cured animals paused only a moment to sniff the air, before running off down the alley, back into the city. Donnie smiled to himself, proud and glad to have gotten rid of one more danger in the already dangerous town, then ran to catch up with his brothers.

Tonight they would celebrate, but he knew there was a lot more work to do.

Chapter Text

Chapter 3:Snake (Snakeweed)

Donnie tucked and rolled as a large vine was shot at his face, narrowly avoiding crashing into the wall of the alley. The turtles had succeeded in finding Snakeweed, but reasoning with him was proving to be a lot harder. “Please, calm down! We’re not here to fight you, I swear!” pleaded the brainy turtle as he had to dodge another attack.  

“Um, Donnie” yelled Raph as he impaled an attacking vine, ripping it off with a squelch,
“In case you haven’t noticed, talking isn’t working! Let’s just spray him already and go home!”

“Yeah!” agreed Mikey as he attempted to wrap a chain around the flailing mutant, “I don’t think he wants to stay a walking salad”.

Donnie shifted uncomfortably, still holding his bo out in a defense position, and considered. “I’d really like another moment to either get consent, or verify that he’s incapable of giving it”.

“Donnie”, reasoned Leo in as level a voice he could manage, “He hasn’t said a coherent word the whole time we’ve been here, and he went straight into attacking us as soon as we showed up. I don’t think he’s thinking the most clearly right now”.

A squealing shriek from the plant mutant reinforced Leo’s argument, and made Donnie feel guilty that his brother was probably right. Even if Snake had been a criminal, he couldn’t help but feel bad that they caused him to lose his mind. Steadying his nerves, Donnie got serious, taking out the sprayer of retro-mutagen and popping the safety cap off. His brothers all sighed in relief that the fight would be over soon. (Not that fighting Snakeweed was normally that difficult, but it was when you had strict orders to not completely cream him.)

“Ok, Snake, I’m going to ask one last time to be sure. I have the cure for your mutation right here, should I use it?” Snakeweed gave no indication that he heard or understood the question, and continued to whip vines around, which all of the turtles had to dodge.

“Good enough answer for ya, Donnie?” asked Raph testily.

Deciding once and for all that Snakeweed was irrational, Donnie aimed the retro-mutagen and sprayed. Fortunately, Snakeweed was a pretty large target, so that made him hard to miss. It was nice to have an easy one for once, just spray in the general direction and that’s it.

When the shot hit its mark, Snakeweed flailed more erratically, a harsh scream coming from the giant plant. Little by little, starting at the head and going downwards, the plant flesh turned a deadish white-gray, and fell to the ground in clumps. Soon, a hand emerged from the pile of leaves and stem, and was soon followed by the head and torso of a raggedy tan-skinned man. Snake blinked, and stared forward dazedly, before bringing his hand in front of his face, wiggling his fingers in wonder.

Clearing his throat awkwardly, Donnie moved to offer his hand to help the recently cured human up, saying, “Um, Mr Snake, sir-” Snake’s head snapped up, and for a moment his features warred between relieved joy and anger, before settling on anger.

“You turtles!” he screamed, rage winning over his continued wonder at having his normal voice back, “Get away from me!” he scrambled backwards through the remains of his old body.

Leo, a more assertive negotiator than the gentle Donnie, stepped up to calm the situation, “It’s ok, Snake, it’s all over, my brother cured you”.

“You’re welcome for that by the way” cut in Raph brusquely, not forgetting that they met Snake when he was kidnapping people.

“Yeah, well, it’s you freaks ’ faults I was a mutant in the first place!”

Both Raph and Leo had a response for that, when surprisingly Donnie stepped up, looking down at the human sternly, “Don’t give us that. You were kidnapping people. We just did what we had to do to rescue your victims”.

“You know what they say about karma” chirped Raph sassily with a smirk.

“Yeah!” added Mikey, feeling somewhat left out. In an aside to Leo, he asked, “Wait, what do they say?”

Amusedly rolling his eyes at his innocent little brother, Leo turned back to Snake, who despite his anger had not moved. “Look, Snake, you did something bad and got turned into a plant because of it. But now you’re human again. Consider it a second chance”.

The leader turned back to his team, their mission finished, “C’mon guys, let’s go”.

Raph gave a sassy wave to the thoughtful/angry Snake, snarking, “See ya, but not really”, before turning and following Leo back up to the rooftops. Donnie gave the ex-mutant a meaningful look, before he too climbed up the nearest fire-escape, his little brother in tow.

Back on the roofs of New York, the turtles all watched as Snake stared after them with an unreadable expression from where they were, then shakily got to his feet and walked away, not looking back at the remains of what had he had been.

“Do you think he’ll take this second chance to heart?” Donnie couldn’t help but wonder out loud.

“Pssh, doubt it. Criminals don’t change” answered Raph, already turning away and ready to go home.

“I don’t know, dude” answered Mikey more thoughtfully, “I mean, I kinda hope so. Anyone can change, right?”

Donnie looked at his brother in surprise, but then turned thoughtful as well. “I guess so, Mikey”.  With that one more wrong righted, the turtles turned towards home.

Chapter Text

“Helloooo?! Sparrow dude?! You around here?!” called Mikey as the turtles were, once again, wandering the sewers searching for a mutant. Fortunately, this time the mutant they were looking for wasn’t a threat. 

“Mikey, you’ve interacted with Malachi the most. Don’t you have any idea where he might have gone?” asked Leo as their searching had gotten them nowhere fast. 

“Yeah, I’ve met him the most, but that was for like one session of Mazes and Mutants. I haven’t seen the dude in forever.”

“It’s a good thing I brought my scanner, then,” said Donnie, waving the device in front of him and looking for any signal of mutant activity. 

“Are we even sure that the guy is still in the sewers?” asked Leo. 

“Yeah,” added Raph, “most humans I know wouldn’t consider the New York sewers prime real estate.” 

All Donnie could do was shrug. Unfortunately, Malachi was a lot harder to find than some of the other mutants. Martin Milton, or in his LARPing alias he went by, Malachi, wasn’t anything like the Squirrelinoids. He wasn’t a vicious unthinking animal, just an innocent, unfairly mutated, young human. That meant that he wouldn’t just stay in one spot because he didn’t know any better how to get out, he would go where he wanted to go. And none of the brothers knew the young sparrow-mutant well enough to know where he would want to go. Which, turtle luck running true to form, led to further hours of fruitless searching through the sewers. The best idea Donnie could come up with was to start where they had first met Malachi and radiate out from there. Of course, that was going off the assumption that he had stayed in the sewers, and not gone to stay somewhere topside, like Spiderbytez and Snakeweed had. So far all they had to show for it was two days of searching, getting covered with sewer gunk, and a slowly developing migraine for Donatello. 

But third times the charm, right? 

They had gone even further out from the original spot, down to a virtual labyrinth of abandoned sewer tunnels, old building projects, and who even knew what. Donnie figured you could probably hide a whole hidden society underneath New York. 

A whole society would probably be easier to find than one lone sparrow mutant , he privately despaired, staring harshly at the device in his hand as if he could force it to do something . He couldn’t help but give a triumphant whoop when his scanner finally gave the barest blip of activity. It might not have even been Martin, and the signal might have been faint, but it was the most indication they had gotten in days that they were even remotely in the right spot. 

“This way, guys!” encouraged Donnie, taking off at a brisk jog in the general direction the scanner pointed, mood lifting as the signal got stronger with every stride. His brothers looked at each other a moment, before following from behind. 

He only slowed down when he noticed the walls of the tunnel looked...off. His brothers slammed into the back of his shell when he stopped suddenly to peer closely at their new surroundings. 

“Donnie, why’d you stop?” asked Leo, trying to follow his brother’s gaze. 

“The walls,” he mused, looking up towards the ceiling, “Something’s off about them. They look more like wood than concrete.” 

Raph rolled his eyes, retorting, “Ok so the City of New York decided to do a little interior decorating. Who cares?” 

Donnie only hummed contemplatively to himself, staring at the walls another moment before shrugging and continuing forwards. 

This time the whole team slowed as the sewer tunnel grew more and more...wrong. As they progressed the walls shifted into straight wooden panels, and the roof leveled out into white, slightly cracked, plaster. As they walked further, Leo paused to stare out of an unsettling window that had appeared, showing the city, but in a way that looked hazy. Unclear. The buildings all there, but lacking detail. He shuddered and tore his gaze away to look at his younger brother and his scanner, instead. 

As if the creepy changing surrounding hadn’t been enough to convince them, the scanner’s blips indicated that they were getting closer and closer to a mutant. As they got closer, they all cautiously got their weapons out as they started to hear voices. By now the scanner was beeping constantly, and the area around them had completely transformed. The tunnel had turned to a narrow hallway, the walls a cracked gray plaster and the formerly concrete floor now covered in a dingy once-multi-colored carpet. Leo shared a concerned look with Raph, them both turning to their genius brother for an explanation. He didn’t look concerned at all, and in fact looked relieved. Glancing at the shifted ceiling he commented, “Looks like we found our mutant. We must be in one of his illusions.” 

From the back of the pack Mikey investigated the spooky hallway, tapping a framed blurry picture and watching it sway. “Weird,” he observed, “This is almost, like, freakier than the medieval dungeon.” 

“Yeah, something about this place seems wrong, somehow,” added Leo, remembering the weird window he had seen before and noticing that the picture on the wall was similarly unclear and fuzzy. “So, guys, let’s get our weapons out, just in case.” 

The team did as he said, except Donnie, who continued to peer at the sensor. A bit walking later and the voice was clearer, and they could tell that it was in fact that of the sparrow mutant they were looking for. They were stopped short by a door that materialized in front of them, the four in the 74 hanging on the door slightly crooked. 

“Haha,” they could hear the young wizard laugh, “Your cooking is always the best.” 

To their surprise, a voice replied, sounding like an older woman, who laughed lightly and replied, “What a flatterer my son is.” There was a pause in-between, like an actor waiting for a cue and the turtles looked at eachother uneasily. The woman spoke again, sounding sly, “If only you could use that flattery to bring home a girl.”

“Maaaaaa,” whined Malachi, though his voice sounded like a contradictory mixture of mortified embarrassment, mirth, and trying not to cry all at once. 

Amidst this dialogue, the teens all looked to the eldest brother, wondering what to do. Leo stiffened his shoulders, setting his face determinedly, and put a hand around the doorknob to open the door. 

The sewer tunnels looked like an apartment. A slightly dinghy but homey looking kitchen spread out in front of them, and they could see a similarly small and comfortable living area to the side. Beyond the kitchen there appeared to be more house, but this was swathed in shadows. In the kitchen they were met with the sight of the familiar Malachi, sitting at a beat up kitchen table with a plate of meatloaf in front of him. And a human woman sat across from him, a cheerful, but slightly blank, expression on her face as she leaned on the table. Swiftly turning her head, she grinned at the turtles, remarking, “Martin! You didn’t tell me you were having friends over!” 

The young sparrow looked at the turtles with confusion, saying aloud, “I wasn’t planning on it.” 

“Hi, Malachi,” greeted Leo carefully, looking at the human woman with caution and some concern. 

The other mutant seemed to recover from his confusion quickly, standing up in his chair and greeting enthusiastically, “Greetings, young turtle! Hast thou arrived to join-eth us for supper?”

“Uhhhh…” stammered the leader, unsure what to say. 

“Malachi, we came here to help you,” Donatello stepped up to earnestly inform the young man, spreading his arms wide and gesturing at the general surroundings. 

Rather than looked happy about this, the bird’s beak turned to a frown, and Donatello’s words seemed to make him panic, “That not be-ith thine usual dialogue,” in a lower tone he muttered to the table, “This hast been a most puzzling first.” 

Malachi’s mother frowned as he did, and he shook his head. 

Donnie took another step towards the table, holding his hand out reassuringly, “Malachi,” the turtle paused, thought about it, and amended, “Martin. It’s alright. We came here to help,” he held up his vial of retromutagen for the sparrow to see, explaining kindly, “This is retromutagen. We can use it on you to make you human again.” 

“Human again?” echoed Martin, dropping his persona’s accent and staring down at his feathery form in detached wonder. As he thought, his face grew stormy again, and he shook his head -- the world around them shuddering for a moment as he did. “No!” he shouted, gripping at his head, “This isn’t real. I’m making you say this!” 

His “mother” grew fuzzy before their eyes, her face switching from an absent smile, to a distressed frown, to motherly concern and back again. The apartment around them similarly grew indistinct, the side rooms filling with shadow until all that remained was the kitchen, lit by a single light. 

“There is no cure,” Martin muttered to himself, pounding his hands against the table for emphasis, “There is no cure, this isn’t real. Don’t do this to yourself again.” 

“Uhh, I think this sparrow mighta turned into a cuckoo bird,” remarked Raph, looking on to the scene with slightly fearful concern. 

Said sparrow looked swiftly up, pointing to Raph as he did, “See, that’s exactly what the real Rapheal would say. I’m getting too good at this,”  he babbled panickedly, leaning his head in his arms against the now-flickering table. “Now I can’t even recognize my own illusions,” he said with a small hysteric laugh. 

The apartment around them grew darker, the walls of the New York sewers filling in around them and the human woman disappearing with a panicked grimace. The area was starting to look normal again, though everything was enveloped with dark shadows that was more than just the results of being underground. 

Donnie looked at the young mutant with sympathy, before his eyes lit up in determination and he walked up to the lone bird with meaningful strides. The sparrow had started to hyperventilate, tears growing at the corners of his eyes and his breath coming out in soft twittering gasps.  The closer Donnie got, the more alarmed and confused Malachi looked. 

Looking him in the eyes, the purple-banded turtle crouched down at the much smaller mutant’s side, placing a steadying hand on his shoulder as he did. “Martin, I’m real, I promise.” He held up the vial in Martin’s line of sight, saying with conviction, “This is a real retromutagen, and it can help you.” 

“Wait, really?” he asked haltingly, looking at where Donnie’s hand met his shoulder and finally coming to the realization this all was actually happening. 

Donatello nodded, smiling reassuringly and his brothers did the same. 

“We can turn you human again, Malachi,” Leo told him, “All we need is an ok from you.” 

“Yes!” the sparrow mutant exclaimed, the settings surrounding them finally turning back to their normal state as he stood up from the block of concrete he had been sitting on. “Yes, please!” 

Donnie went to give him the retromutagen but was stopped surprised when Mikey threw an arm in his path. “Wait, D!” he said, narrowing his eyes at Malachi, “How do we know that that’s actually Malachi, you know? He’s not talking all medieval-ly.” 

Everyone shot the youngest turtle a look at that, Raph pulling Mikey roughly aside as he did. “Pretty sure we’ve got the right dorky sewer sparrow, Mikey,” he said. Thinking on it, he added, grumbling, “At least we better. I’m so done with looking through the sewers all day.” 

Malachi laughed nervously, commenting, “I’m pretty sure I’ve never made an illusion of myself, before,” his beak twisted thoughtfully, and he tapped at the general area of his chin, “I’m not even sure how that would work. Sounds like it’d be a bit of a headache.” 

Donnie prepped the retromutagen, pulling on gloves and carefully sucking the viscous semi-liquid into a dropper to not waste any of it. It was a relief to finally have someone receiving the cure be consenting and still. It made it so much easier to use a carefully measured dose. 

Retromutagen in the dropper, Donnie held it aloft, explaining to Martin before he did anything, “Now, just so you know this is pretty much permanent. And also painful, for about a minute. It’ll make you human again, just like you were. Which means you won’t be able to use your illusions anymore,” he warned cautiously. 

Malachi whistled dismissively at the warning, “That’s alright.”

“But, dude, your sick LARPing seshes,” posed Mikey, wide-eyed at the thought of removing such possible awesome creative experiences from the world. 

“Ah, a true Dungeon Master weaveth a gripping adventure fromst his wordes, not magical powers,” the role-player pronounced, posing proudly. Posture deflating, he fiddled with his hands, adding in his normal voice, “Besides, I miss my mom and she needs me. No way I can live with her like this,” he stated with a sad warble, gesturing at his whole situation. 

The tallest turtle nodded sympathetically with a small smile. Gesturing with the prepared dropper, he asked, “So are you ready, then?” 

He was about to say yes, but then paused, wringing his hands again. “You said it hurts?” he asked the scientist worriedly

Donnie grimaced, wishing he could find a way to fix that side effect. But there was no real way to change the fact that morphing a being’s entire physical structure inside and out was a process that was going to hurt. He made a mental note to maybe try and bring some pain relievers with him next time they found one of the sentient mutants that needed the cure. For now, though, he could only say apologetically, “Yeah. But--” he quickly reassured, “every test says that it’s only painful for a few seconds, a minute at most.” 

“Ok, ok, in that case,” he took a deep breath, steadying himself before replying, looking up to Donnie with confidence, “I’m ready.” 

“Alright, then,” Donnie started to move the dropper over the smaller mutant’s head -- Malachi closing his eyes in preparation as he did -- but paused as his gaze flickered to the sparrow’s wooden leg. “Um, actually, you’re probably going to have to take that off, first,” he said awkwardly, gesturing at the make-shift prosthetic with his head, “It might cause some problems while your body is shifting. Could cause damage.” 

Malachi opened his eyes, taking a moment to realize what the turtle was referring to. “Oh,” he said with a surprised chirrup. Leaning over to untie the prosthetic he mentioned, “I suppose that makes sense.” While he struggled to untie the whittled wood from his leg, Leo looked on in minor horror. 

“Mutating didn’t make you lose your leg, did it?” he asked in concern, knowing that all things concerned they had seen far more brutal effects from mutation but still, losing a leg ? That would be so strangely specifically cruel. 

To his relief (?) the small bird waved off the concern as he took the prosthetic off and set it aside, “No, no , no. This,” he gestured to his feathered stump in the place of the wooden leg, “Was already, ah, like this. Mutating just made it so my old prosthetic didn’t fit right anymore.” 

“Ah, that’s, good, I guess,” Leo floundered, not having met anyone missing a limb and not certain he was going about it the right way. Martin didn’t seem to mind though, and sat down -- once again readying himself for the retromutagen. 

Donnie hovered the dropper over him, counting down as he did. “In three, two, one,” with a squeeze, his distributed a sizable drop onto the mutant’s head, holding his breath in anticipation despite knowing full well the retromutagen would work. 

On the ground, Martin squirmed and screamed as the reverse-mutation began, working its way through his body. His feathers seemed to suck back into his skin, the pale pink human skin stretching out over it in its place. His beak softened and melted back into a human nose and lips. 

In less then a minute, the process was over, and Martin Milton was back to his human self. He stared at his human hand wonderingly, running it over his face and gasping in joy to feel a pudgy human nose instead of a hard sparrow’s beak. 

With a wide smile, he tried to shoot up to his feet, stumbling on his one leg as he did. His arms wind-milled, but he was caught by an equally smiling Donatello before he could fall back to the ground. Tears of joy pricked at the side of his eyes, and he stared gratefully at the taller turtle. “Thank you,” he said empathetically. 

Donnie could not stop smiling. This was why they were doing this. No matter how much effort it took to find all of the mutants, no matter how much pain it was to make the retromutagen, he knew that returning people to joy, giving them their lives back would make all of it worth it a thousand times over. “You’re welcome,” he replied. 

The trek back up to the surface was a little longer than expected. Between not having used human limbs in a while and being short a leg, the ex-mutant made slow time through the vast sewers up to the street. But he didn’t complain once. Instead he talked cheerfully of seeing his mom again, and that he would have to call his roleplaying buddies when he got back. 

The turtles at last dropped the young man at the doorstep of his apartment. Martin clutched the edge of the door to steady himself, waving aggressively at the turtles with his free hand as he did. “Many gracious thanks, turtle friends!” he declared. “Mayhaps we can meet again for some Mazes and Mutants?” Throwing his cape over his shoulder, he ended, “Until then, farewell!” Turning around, he hobbled at a surprising speed into the building. “Mom!” they heard his retreating voice call. 

“Martin, you’re home!” cried the same voice that the turtles had heard in the sewers, though this one was choked with tears and love and they knew there was no copying the real effect of a parent’s love. 

Amidst the sounds of the happy reunion, the turtles headed back into the shadows. Except for Donnie, who lingered to listen to the tearful back and forth of the two Miltons, before, he, too followed with a hopeful smile.

Chapter Text

The turtles stared in confusion at the scene before them. When they had followed the mutant tracker to the original home of Vic “Spiderbytez” NoLastName, they had gone in expecting a fight from the ill-tempered man. Instead as they (read: Raph)  kicked in the door and barged into the apartment, they were immediately shushed by the large spider man sitting attentively in front of his tv. 

“Keep it down, frogs, will ya? This is an important race for me!” the mutant barely even looked away from the television as he said this, instead he started to shake his fists, upper appendages curling anxiously as he muttered to the screen, “C’mon porker, I know you can beat X. Get that underdog victory and make me a ton of money!” 

“Ooookay, I’m not the only one totally confused right now, right?” asked Mikey carefully. 

His brothers all shook their heads, equally puzzled at what the heck was going on. Soon enough, Raph stomped in front of the tv and brought himself face to face with the larger mutant, doing his best to stare him down despite the fact it was hard to know where to stare to intimidate someone when they had six eyes. But ninjas weren’t quitters so Raph did his best anyway. “Hey,bug breath, we’re here to give you a cure you don’t deserve so you can be a terrible human instead of a terrible mutant.” Rather than listening, the spider’s eyes looked over and around Raph to keep track of the events of the tv. The turtle moved to block his line of sight again, glare harshening, “Hey, you got webs in your ears? We've got a retromutagen. You wanna look away from the idiot box for two seconds maybe? It’s gonna rot what little brains you have left.” 

“Raph, we didn’t have to fight the guy, do you really have to keep antagonizing him?” Leo groaned. 

Raph gave a wide sarcastic shrug. 

“I think he’s just disappointed he didn’t get to punch anything,” suggested Mikey with a grin. 

“Except the door,” muttered Donnie as his two cents. 

“Hey!” shouted Spiderbytez, finally turning slightly away from the television set (though his upper eyes continued to linger on the screen), “What part of ‘shhh’ don’t you frogs get?! What were ya, raised in the sewers?”

“Well actually--” started Mikey before being completely cut off by Raph. 

“Look do you want the freaking retromutagen or not!” retorted the hot tempered turtle. 

“Hard pass, goodbye,” harshly returned the taller mutant, waving the turtles away. 

“Wait, what?” replied Raph, echoing his brothers’ thoughts with wide eyes. That…had been an unexpected response. The turtles all traded questioning glances.

“But, Vic,” hesitantly offered Donnie, being sure to call the once-human by his actual name, “This retromutagen will make you human again.” 

“Whatever,” the spider scoffed. When nothing but heavy confused silence followed, he groaned, finally pulling fully away from the tv to face the group of ninja turtles. “Look, before, I was a bald fat nobody with no money.”

“Well, you got that part right,” muttered Raph, who was quickly shot down by glares from everyone but his youngest brother. He held up his hands in half-hearted surrender then sarcastically gestured for the spider mutant to continue. 

“Anyway,” Vic carried on, “you know how much I’m making in the underground mutant community now? And what’s a landlord gonna do, kick me out?” He gave a sibilant snort at the idea, and added self-importantly, pointing roughly towards the floor to accentuate his words, “S’long as I got the rent, I get the room, who the hell cares what I look like? And if he refuses me I got plenty a’ other ways to get a place to crash.”

The turtles stared, dumbfounded. Did this guy really care about money more than being a mutant? And after he nearly killed them all for changing him into one in the first place? Some people. 

Waving the turtles away, the giant spider added, “I got cable, I got fans, hell, I have a reputation , frogs.I’m good where I’m at. So why don’t you take your freaky jello and crawl back to your pond, huh? Leave me alone, I got a race to bet on.” With that, the spider turned to watching his tv (which was playing some kind of obstacle course…game show? With mutants as the contestants, which, ok, that looked kind of shady), and talked to them no more. 

Struck uncharacteristically speechless at the greedy man’s decision, Raph just threw his hands in the air and stomped out of the door the way that he came, Mikey following right after. 

Donnie looked between the spider mutant and the container of retromutagen a few times, before shrugging in confusion and stowing the important ooze away. Like he had said, whether someone would be “cured” or not was their decision. And, honestly, this saved retromutagen which was something he was a bit grateful for. He turned towards the door to follow his brothers out, but paused a moment to watch the “race” that was happening on tv that Spiderbytez was apparently now making a living off of betting on. He cringed as something on screen exploded and the spider mutant cheered. Lingering under the door frame, the purple banded turtle turned to his older brother. “Should we do something about this underground mutant sports ring?” Donnie asked, not sure if that was considered a threat or not. 

“Ummmm,” replied Leo, still processing the whole encounter. Shaking his head he said, “Nah, I’m sure it’s…fine.” 

“Can you guys stop lingering with bug butt!” shouted Raph from the roof outside, “I wanna just get home already!” 

“Yeah, coming!” called Leo in return, patting Donnie on the shoulder reassuringly before leaving the apartment. 

Donnie took one last look at the befuddling apartment, tv, and occupant, then shook his head and followed his brothers out. He jogged to catch up with his family who were already on the roof ahead, unable to help himself from clarifying, “Spiders are arachnids, not bugs, Raph,” 

“Whatever,” the older brother huffed, “I literally could not care less.” 

Another mutant found and (sort of) dealt with, the turtles turned around and once again returned home.