Dad says, "April, no."
April stares at him in utter shock. Something sour seems to slide down her throat and curdle in her stomach. "But—"
"I'm sorry about the turtles, honey, I am," her dad says. "I really am."
"If you were really sorry, you wouldn't say no—" she says, voice rising, but Dad's voice rises too, carrying over hers:
"But it's just too dangerous, sweetheart, the aliens are bad enough, but this Shredder—"
"—I can't just leave them, Dad, they're my friends—"
"April Marie," her dad says, in a voice that stops April's in her mouth. "For once you will listen to me and do as I say."
The sour feeling in April's stomach only grows as she stares back, mute, her hands shaking. Her father pauses, as if to make sure that she's going to stay quiet, before continuing. "This man is dangerous, honey. He's a- a crime lord. They're involved in all kinds of things you don't need to know about. And this business with new mutagen—no, April. No. I'm sorry, but I'm putting my foot down. Stay away from this."
"I'm immune to mutagen," April says, the words tumbling hot and bitter out of her mouth.
"You're not immune to guns, April! Or swords!" He stops, breathing heavily, and his eyes shift from side to side. He swallows, his hand drifting up to touch the side of his neck. "I'm sorry about your friends," he says.
"They saved me. Over and over," April says. "They— Donnie saved you, Dad, twice, and they never gave up, not ever—"
"I said no, April."
He's looking back at her now, not watching the fly zipping around the room or staring out the window, and his expression has hardened. April stares back. She can count on the fingers of one hand the number of times he hasn't let her have her way, all the way back to the day of her mother's funeral. And every time he didn't let her have her way, he looked at her like this, trying to be stern, trying to make his eyes like ice.
Once upon a time, she might have pouted or whined or kept wheedling, cried or begged, thrown herself to the ground and refused to budge. All that was before, though. Before she had to get along without her dad. Before she had to stand up to the Kraang and their probes in her brain. Before she became a kunoichi.
April runs her thumb over the calluses her tessen left on her palm. She remembers Splinter telling her that a kunoichi's best weapon is deception.
Her father has no idea what she's capable of.
She blinks her eyes and lowers her chin. "Okay, Dad," she says, soft and sad. "I understand."
Her father lets out a relieved breath and pats her shoulder. "I really am sorry," he says.
She looks up at him through her bangs. He's giving her an anxious, wavering smile.
She gets it. He just wants her to stay safe. He doesn't understand that there are things more important to her than safety.
"Damn, Red," Casey says, later, when April tells him what her father said. "What're you gonna do?"
She frowns at him. "What do you think I'm going to do? I'm going to figure out this retro-mutagen. I just need to hide it from my dad, that's all."
Casey nods, unusually serious. "You go, Red. I got your back." He breaks out in his usual smirk. "You know you'll get the goal with Casey Jones running interference."
April laughs and punches him in the shoulder, and for a moment things are almost normal again.
#
Everyone looks at her differently now. The lower-ranking Foot ninja shy away from Karai, not meeting her eyes, but sneaking looks at her behind her back. Shredder's lieutenants are different; their inhuman eyes follow her all the time. Tiger Claw stares at her from his towering height, as if she's an interesting piece of prey. Bradford, or what's left of him, slinks into the dojo to watch her train, as if he is sizing her up. She catches Xever's round fish eyes watching her wherever she goes.
Karai holds her head high and her shoulders back. She strides around the compound as if nothing has changed, as if she had never been locked in a cell for having the temerity to question her paternity. She trains, she goes on missions as she is ordered, commanding the ninja and their robots. She is never paired with one of the other lieutenants. No one seems to have observed her unauthorized departure, when she found April O'Neil and her friend. Karai does not allow herself to relax, not quite, but her confidence grows by degrees.
One day, Xever breaks the silence. "It could have been you, you know."
They are passing in the corridor, Karai on her way to dinner. She pauses in place. "Excuse me?"
"In the vat," Xever says, rubbery lips curling back to show his sharp teeth. "You could have ended up like us."
Xever used to flirt with Karai, back when he was a man. Back in Tokyo, before she had ever been to New York. It seems like a long time ago now, but she still remembers. She had flirted back, a little, quietly, discreetly, not under her father's stern eye. Xever had never tried anything beyond smiles and compliments and offering her a cigarette when she was fifteen. She had liked him; they had been friends, as much as anyone had friends in the Foot clan. He was not a ninja, but he respected their ways, did her father's bidding, and Karai knew very well that Xever was useful to her father because he would do things even the ninja would not do.
He respected her, too, offered to show her a trick or two from street fighting, and acknowledged her skills. Not like Bradford, who treated her like a little girl playing dress-up, even though he had started ninjutsu much later in life than she had, had had to unlearn old martial arts to learn their ways. He always underestimated her, but she would not make the same mistake. She had stolen into the dojo to watch him, hiding herself in the rafters, silent as a shadow. Sometimes Xever had even come with her.
It had been strange to come to New York and find the pair of them so changed. It is difficult, even now, to see the lean face and dark eyes and blade-like smile she once knew in the face of the fish.
But this is her opportunity, so she lets her mouth turn down, lets her eyes soften, and says, "I know. I know it could have been me. I didn't really understand before, Xever—"
He snorts, wide mouth opening to let out the puff of air. "You didn't care to understand."
"I didn't," she agrees, ducking her head a little. She doesn't apologize; she's not good at apologies. Xever would suspect one in a moment. "I wish— do you think there's any way for you to be human again?"
Xever huffs again. "Stockman says he's working on it."
"Oh," she says, and lets the word lie there. She knows how little respect any of them have for Stockman.
Sure enough, Xever's round eyes roll. "Probably just keep it for himself," he mutters.
"If he doesn't screw it up," Karai says.
Xever's eyes roll again, and he laughs, a strange sound coming out of that month. "That is hardly likely, no?"
She gives him a quick smile— "Not very, no"— and lets her expression grow pensive again. "Now I suppose the turtle could have done it—"
"And how are your new pets?"
Karai shrugs one shoulder. "—or if my father really wanted to find a cure, maybe he'd find a real chemist or geneticist, but—" She starts to turn away.
"And doesn't he?" Xever demands, planting his robotic feet.
Karai looks back over her shoulder, deliberately widening her eyes. "What do you think?"
A flicker passes over his face that she can't read. But it's obvious, isn't it? The mutants are dependent on the Foot clan, and stronger than they were. Why should he want them to be restored to their old selves?
After she lets that sink in, Karai glances swiftly side to side and draws close enough to Xever to whisper, "But I promise you, someday, when I take over the Foot clan—"
"You presume much," Xever hisses back.
Karai draws herself up. "I am in my father's favor again, am I not?"
"True," he allows. "But your father is still vigorous, girl. You will not lead this clan for a long time."
"True," she returns. "But I keep my promises."
She turns again, and this time he lets her go. She does not let herself smile. She has planted a seed, that's all. Let Xever think it over. Let him consider his loyalties and where his best advantage lies.
Let him be the one to come to her and say, as if it were entirely his own idea, "What if we removed Shredder?"
#
Donnie's notes are impossible.
Oh, he took meticulous notes on everything, but the paper journal just has records of things done, quantities of components and the like, and it's heavily abbreviated. On top of that, the marginal notes are half in English and half in Japanese, which April only speaks a few words of. That means she's going to have let Karai read them to see if there's anything important in those notes, and she hates the idea of letting Karai get her hands on these notebooks. They're just so... so Donnie. The earliest ones must have been cribbed out of the trash, because there are weird stains on the cover and some of the pages in the front are missing, and someone else's handwriting is crossed out, the notebook relabeled and dated in Donnie's blocky print. The later ones are ones she bought for him, so they're neat and square and almost unblemished, except for occasional spots that look like dried ice cream or pizza grease, even though every notebook is labeled "MIKEY DO NOT TOUCH" on the front. There are random doodles on the pages, too, including little stick-figure illustrations of her—she can tell because of the ponytail and the fan in her hand. If she can't figure this out, these notebooks and the tessen might be the only things she has to remember him by, or any of them—the best friends she ever had, and she didn't even say goodbye properly the last time she talked to Donnie—
When she thinks about things like that, April finds a lump in her throat, and her eyes get too blurry to see what she's trying to read. So she tries really hard not to think about it, and mostly succeeds, except for when she throws herself in bed at night and tosses and turns, too wired from the day's dose of caffeine to fall asleep easily.
What's worse than the paper notes are the files on Donnie's computer, where he was doing all the theoretical work. That's where the real stuff is. April could probably duplicate Donnie's retro-mutagen from the lab journals, but to tweak it? To change the formula so it'll work on the altered mutagen Stockman dosed the turtles with? For that, she's going to need the theory, and those files are encrypted.
So now April has to be a codebreaker as well as a geneticist, and she's been trying, but every time she thinks she's getting somewhere, she gets a string of gibberish and has to go back to square one. She's been at it for weeks now, and meanwhile the guys are sitting in a terrarium in Karai's room.
April remembers how long it took Donnie to invent the retro-mutagen in the first place, and it makes something cold trickle down her spine. She wishes so much that she'd listened better, or tried harder to stay awake in the lab and help. Something, anything, so that she'd have more of a clue what she was doing now. Karai's willing to help, but she knows a lot about ninjutsu and not much about science, so her help is limited to stealing the mutagen samples April needs. Casey can't help much either, though he brings her food and energy drinks and runs interference with her dad.
April mostly can't work at home; she keeps her notes and the files she copied from Donnie's laptop in her locker at school, and takes to working in the library whenever she can. Sometimes she goes down to the lair, but it's much, much too quiet and cold and lonely down there. She comes to have a usual corner that she stakes out, setting up her computer and the papers around her like a fortress. Usually no one disturbs her.
This day she's too busy trying yet another method of decryption, and while the program runs, she flips through one of the notebooks, looking for anything useful, and freezes when she sees "D + A" written into a margin. April's eyes start to sting. She shoves the whole stack of notebooks away from her, hard enough that some of them fall to the floor. Her computer beeps at her softly: another failed attempt. April grinds her teeth and rubs her eyes. She doesn't know what to do next. She's stuck, spinning her wheels uselessly, and Casey's only interested in science that blows up, so he can't help, and her father won't help, and the turtles are snakes, and—
It's all too much. When her father was taken before, at least she had the turtles to keep her company, and when her father was mutated, she had her anger to hold onto. Plus, she knew the turtles were out there, all the same, keeping up the fight and the search when she couldn't. It comforted her even when she was angry with them.
April's vision blurs. She pushes herself away from the table and reaches, blindly, for the fallen notebooks. A familiar voice says, "April, are you all right?"
"I'm fine." April hunches her shoulders. Irma's presence just reminds her of how she's screwed that up, too. Irma still tries to be her friend. It's not her fault that April has secrets to keep.
"Let me just help you pick these up," Irma says, crouching down on the opposite side of the heap of papers from April.
April wipes her eyes again. "No, that's fine, I've got it," she says, but she reaches for the stack of notes too late. Irma's already gathering the papers into her hands. April hesitates; she can't very well just yank them away.
There's a pause where she hears the rustle of the papers in Irma's hands. She holds out her own hand, hoping that Irma will just turn them over, no problem.
But Irma says, "April, what are you doing researching mutagen?"
"Nothing!" says April, too high-pitched. She scoops up a couple of notebooks, and a horrid thought crosses her mind. "What do you know about the mutagen?"
"What do I know about what mutagen?" Irma says. When April looks up, finally meeting her eyes, she's frowning, and pushes up her glasses with one hand. "Mutagen just means a substance that tends to cause alterations to an organism's DNA. But that kind of thing is dangerous, April, why would you be messing around with it?"
"I know," April snaps. "Believe me, I know it's dangerous. But I have to do it, and you wouldn't believe me if I told you, so why don't you forget we even had this conversation?" She reaches for the journals.
Irma lets her take them, but she doesn't go away. Instead she hesitates while April gathers up all the notebooks—she's going to have to sort them out again and put them in order, yet another thing to do—and then says, "Is this about your dad's disappearance?"
"No." April shoves the notebooks into a stack.
"Because, April, I'm- I'm sorry about what I said, back then—"
"It's fine." Bad enough the police hadn't believed her, but Irma was supposed to be her friend. They were supposed to trust and believe in each other. She hadn't even talked to Irma for nearly a month after it all happened, and they hadn't really made up until April had her father back. The first time, anyway. "It doesn't matter," April says, straightening up to put the stack of notebooks onto her table. The encrypted gibberish still stares at her from her laptop screen.
Irma straightens up with her, looking earnest and worried. She tucks a lock of dark hair behind her ear. "Then— is this about your secret friends again? Because I've hardly seen you in the last few weeks, and you look—"
"It's not what you think," April says, tightening her mouth into a firm line and turning away.
"I'm just worried about you, April, all that stuff with your dad, and now these friends— are you in some kind of trouble? Because if they're dangerous—"
"Don't even," April says. She keeps her voice low, remembering she's in the school library, but there's anger pulsing under her skin. "It's not me who's in trouble, it's my friends, and I'm the only one who can help them, so I'm not going to give up." She turns her back, pointedly, hunching over the laptop again.
There's a moment of silence before Irma says, "And that's why you're researching some kind of mutagen?"
"Just let it go, okay?" Since Irma won't stop hovering behind her shoulder, April starts shoving the notebooks and her notes into her bag.
"Maybe I can help, though. Is that some kind of cipher? Have you done a character frequency analysis?"
"Yes, what do you think I've been doing?" April snaps, whipping around to glare at the other girl. "It's not helping. I tried that, and I just keep getting mixed-up characters—"
Irma holds her ground. "Have you considered that maybe there's a transposition cipher and a substitution cipher?"
April stares.
"Of course, it would help a lot if you knew what the transposition key might be," Irma says, adjusting her glasses. "The key is used to divide the text into columns, and then it's scrambled based on the order of letters in the key. Do you know who ciphered it? What might they pick for a key? It's probably not too long a word, should be something easy to remember. Five or six letters, maybe?"
It doesn't take April more than a moment to think of a five-letter word Donnie might have chosen. Her cheeks grow warm. "I might have an idea," she whispers. "How do we use the key?"
It's not difficult to write a script that will use the key APRIL to rearrange the text, and then, when April tries the character frequency analysis again, words start to appear. Real, beautiful words. They start swimming before April's eyes, and she buries her face in her hands.
"April? Are you okay?"
April swallows down a sob and wipes her eyes. Irma is peering down at her anxiously. "Why?" she whispers. "Why would you—"
Irma bites her lip. "You're my friend, April," she says. "And you've been looking just miserable, lately, and I know I haven't always been the best friend, but I want to help you if I can."
April takes one slow breath after another, nice and even, like Sensei taught her, trying to get her tears under control. "We have to get to class," she says, "but can you meet up after school?"
Irma nods, wide-eyed.
April breathes out, feeling the tightness across her chest loosen just a little. "At the noodle shop. Murakami's. I'll— I'll explain. I'll explain everything."
Author's Note: For the purposes of this story, Irma is a real girl.