"So..." Casey says as they hurry down the sidewalk. "Quick thing you should know, my friends are mutants too."

Shadow nods. "Unsurprising."

He blinks. "Huh? Why?"

"You got excited when I revealed that I was a mutant, which...in my experience, isn't normal. I figured you had seen mutants or at least knew of them," she admits. "Two, most people would just go to a hospital, unless...your friend couldn't, for some reason."

"Maybe he doesn't have a few thousand dollars to spare for an ER visit."

She lets out a soft breath of a laugh. "Good point. But...?"

"Yeah, you're right," he says. He ducks into an alleyway and moves to a manhole cover, squatting to open it. "They live in the sewers. Hope you don't mind the smell."

"I can't smell."

"Damn, really?" She nods. He exhales as he drags the manhole cover off to the side. "That sucks."

"Welcome to my life."

----------

"So what kind of mutants are they? Your friends?" Shadow asks as she and Casey keep moving through the dank sewer tunnels.

"It's a mix," he says. "Four turtles, a wolf-raven, a cyborg, and a rat."

He turns down a separate tunnel and cringes as he hears a rat squeak and race off into the darkness. He looks back at Shadow, moonlight from the grates occasionally letting him see her more clearly.

"Like a big family, huh?" Shadow asks.

"Yup! It started with just the turtles and their dad and then they just kept making friends and the group got bigger."

"How nice."

He isn't sure whether she's being sarcastic or not. Her voice is so monotone that it's hard to tell.

"How did things at school go?" she asks. "After our...talk."

"Oh. Yeah."

He hadn't given it a second thought since then. So much happened with Raphael and Destiny, the warehouse, Beast Mode and the attack—it's like he hasn't let himself breathe since.

He sighs and reaches to scratch the back of his head, wincing as his fingers brush over the goose egg forming there. "My friend had evidence that I didn't start the fight, so they let me off with a warning."

"Really?"

"Yeah, and some stupid extra assignment about 'finding a healthy outlet' or something. They want me to find a place to volunteer at," he says. "I'm pretty sure they just want to keep me busy so they don't have to spend any more energy on me."

Now that he's letting himself think about it, that ever-present feeling of foolishness cloaks him again. He should have taken those papers from April and thanked her instead of pushing her away. He couldn't call her, not now, and not to ask for her help. Not after how he treated her.

"Hm. Do you have the freedom to choose where?" she asks.

"Probably? Ugh." He groans and twists his neck back and forth, stretching it. "I have 'til Monday, at least. No clue what I'm gonna do." Maybe that inner-city kid thing?

She lets out a noncommittal hum but says nothing more.

Conversation dwindles, but their speed doesn't. The closer Casey gets to the lair, the faster he moves, urgency building, and the shadow girl keeps pace. It's only once they near the bright lights that signal the entrance to the lair that she falters.

Casey glances back at her, confused for about a split second before his brain kicks in. Oh, duh, light! She said something about how sunlight isn't great for her, but what about artificial light? Would that be okay?

"So..." he starts, pinwheeling his hand a little.

"I'll stay in your shadow," she says. "Don't worry about slowing down; I can keep up."

He exhales. "Okay, cool. I was wondering, you know, if..."

She shrugs. "Artificial light is okay for short periods, but it's exhausting. I'm going to need my strength if I'm gonna help your friend." She casts a sidelong glance at the lair and adds, "Besides, after what you just endured, it'd be better for you to ease them into my arrival. Got it?"

"Loud and clear."

"Great. See you soon."

She melts into the shadow trailing behind him, melding into the shape of his dark silhouette. He glances at it for one more second before he heads into the lair.

For the most part, things are as he left them. Leonardo paces in the living room while Destiny sits nearby, watching his movements with tensed shoulders, so still that she barely shifts a feather. Michelangelo spars lightly with the punching bag and Casey admits, it's weird to see the kind-hearted turtle taking part in one of Raphael's favourite pastimes.

"Guys? I'm back!" Casey calls as he pushes through the turnstiles.

Leonardo perks up, rushing from the living room pit with Destiny close behind him, although she still seems wobbly on her feet. Michelangelo gets one more solid punch in before he joins them.

"Well? Where are they?" Leonardo asks. Stress keeps his brow and voice pinched.

"She's...uh..." Casey darts a look at his shadow. Maybe he should have scripted something before coming in here. "So here's the thing—"

He hears the laboratory door creak open and Sarina appears, eyes bright and hopeful. "Where is the expert, Casey? Should I go get Donatello?"

This is a lot of pressure and Casey isn't even the one doing the helping. He feels a sharp prick of cold against his heel, right through his sneaker, and he suppresses the urge to glare at his shadow. Sarina keeps staring at him. They all do. Donatello must be with Raphael.

"I don't know how to explain, but just give her a chance, okay?" he explains. "Shadow? You mind coming out?"

She materializes in an instant, forming just behind him so she can keep hiding in his shade, arms crossed and an expression of bored neutrality on her face. The tension in the room spikes, Destiny tensing as she moves her feet into a ready position while Leonardo's hands form into fists, eyes narrowing. Michelangelo raises an eye-ridge.

Shadow doesn't react to any of their movements until Sarina raises her hands, palms starting to glow, and her expression flickers with unease. Casey holds his hands up, keeping Shadow behind him as she hovers a little closer to him, cold creeping along his back.

"Woah, Flash, hold on!" he pleads. "She can help Raph!"

"How do we know that she isn't the one who set Beast Mode on us?" Sarina asks, eyes narrowed despite her calm tone.

"Frankly, I'm appalled you'd even suggest that," Shadow cuts in, raising one finger as she peers over Casey's shoulder. "Also, I'm literally your only chance to save your friend. Do you want to risk it?"

Sarina's hands stop glowing in an instant, her face mellowing as she drops her hands to her side. "No, I suppose I don't."

"You're sure you can help him?" Leonardo asks.

"I'll try. I will need to look at the wound," she replies. "Care to take me to him?"

Leonardo eyes her for another second before he nods, gesturing her to follow him, and Shadow slowly drifts around Casey, giving him one more look before they walk away. As they disappear, Michelangelo, Destiny, and Sarina focus their attention on Casey again.

"So...how do you just happen to know a shadow mutant?" Destiny asks.

"It is quite fortuitous. Or suspicious. It depends on how you look at it," Sarina adds.

Casey flicks his head, moving his bangs from his eyes. "She goes to Roosevelt. We crossed paths a few times this past week. No biggie," he says with a shrug.

"No biggie?" Michelangelo repeats. "I mean, it's kind of a big biggie, because now Raph's gonna be okay!"

"Maybe," Destiny mutters.

"Wolfie, dudette, have some faith," Michelangelo says, pressing his hands together in a praying motion. "The universe is, like, totally bringing us some good mojo."

Sarina's eyes flash as she sighs, pressing her fingertips to her temple. "This is yet another mystery to piece together. New mutants, a garage with security that does not match the contents within, new mutagen..."

Footsteps come from nearby and they look up as Donatello emerges from the hallway, looking shocked, mostly confused.

"Casey knows a shadow mutant..." he asks. "How?"

"Pure dumb luck," Destiny answers.

Casey opens his mouth to refute it, but stops. It's kind of true, he guesses. Fun coincidences all around.

"Donatello, would you accompany me back to the lab?" Sarina asks. "I want to look things over again."

He nods, stifling a yawn into his hand. "Okay, but then you're getting some sleep." She doesn't agree or disagree as she heads back to the lab, and Donatello perks up. "Oh, Casey, your friend asked for you."

"Me?" he repeats. "Why?"

"She didn't want to say. She's kind of vague."

"Yeah, I've noticed."

He starts towards Raphael's bedroom. In the hallway, Leonardo stands sentry outside the door, jaw clenched and arms crossed. Casey approaches, hesitating at the door as soft voices come from the other side. Leonardo looks ahead, although his gaze occasionally flickers towards the door.

"...healing hands," Splinter's low voice comes first. "We had hoped it would slow whatever poison has afflicted him."

"I'm impressed," Shadow says. "It isn't poison though. I don't know what it is, but it isn't that."

"Nonetheless, I am glad you are here. We have not come across someone like you before."

"That doesn't surprise me."

Casey knocks on the bedroom door and their voices halt. Then, Splinter calls him in, and he opens the door.

It's like a wave of sickness hits him in the face, the stench of rotting meat making his stomach curl. He wonders if Shadow has any idea how lucky she is that she can't smell. Raphael lays under his blanket, still as stiff as when Casey last saw him, his dark green skin far too pale and coated in sweat. His arm lays limp at his side, soiled bandages bundled up in the trash can next to his bed.

Casey wishes he hadn't looked at Raphael's arm the second he does so, but then he can't look away. It's turned purple, black veins spreading out from the four stitched wounds; it's like only his arm has started decomposing despite the obvious deep freeze hurting him so badly.

"Casey," Splinter says.

Casey snaps out of it, looking up at him. "Yeah? Sorry, it's...uh..."

"I understand. It is not pleasant," Splinter says. His whiskers twitch, ears pulled back. "Shadow has requested your help. I will...leave you to it." He takes a few steps to the door as Casey replaces him at Raphael's bedside, only to turn back and eye them both. "I cannot thank you enough for coming here."

Shadow nods. "Please remind the others not to disturb us. I need to concentrate."

Splinter affirms her request with a nod of his own before taking his leave.

When they're alone, Casey gives her a confused look. "Why me?"

"You're strong, and I'm the most familiar with you," she says. She floats closer to Raphael's arm, eyeing it with a slight grimace. "What I'm about to do won't be pleasant for Raphael or me," she says, grim. "I need you to hold him down while I extract the infection from him."

He gawks. "Extract the infection...you can do that?"

"Your faith in me is stirring," she mutters. "Hold him down."

Casey eyes Raphael for a second. The turtle is as comatose as can be and hasn't moved since Beast Mode's attack, but he takes her word for it. He climbs onto the bed beside Raphael, bracing his arms against his plastron. He looks up at Shadow and nods.

She takes a deep breath and her eyes disappear as she closes them, leaving her as nothing but a black patch. She places her hands on the decaying wounds crossing Raphael's arm and, after a second, her fingertips start to glow.

Or, Casey guesses they're glowing. It's the only way he can think to describe it. A shadowy aura extends from her fingertips, but there's this halo of white light that separates her fingertips from the aura itself. The shadows seep across Raphael's arm, coating it like paint.

Raphael's eyes snap open as he sucks in a sharp breath, thrashing away from Shadow's hands, and Casey nearly bites his tongue at the sudden movement. He throws the rest of his weight against Raphael as he groans, struggling, but Shadow doesn't back down as more of the aura spreads.

"Keep holding him," she whispers, her voice a distant echo.

Raphael lets out a strangled cry, staring up at the ceiling with pinpoint pupils, and Casey can do nothing but pin him down. He looks up at Shadow, questions on his tongue, but he freezes when he sees her work taking effect. Wisps of darkness float from the shadowy "bandage", piece by piece, faintly outlined in purple, wiggling and twisting like worms as they crawl into her fingertips. She winces and flickers, but keeps going as the patch covering Raphael's arm starts to shrink.

Raphael's expression twists into a pained grimace, eyes darting back and forth without actually seeing a thing as he keeps fighting to get away from Shadow. Casey almost smiles. Even like this, Raphael is a fighter to the core.

The aura has almost disappeared and, beneath it, Raphael's wounds couldn't be more different. Four clean lines, puckered skin held together by Sarina's neat suturing without a hint of pus or bruising.

Another two seconds and Raphael stops thrashing. He lets out a long breath, eyes rolling back before they slide shut, and Casey slowly backs off. Raphael's colour has already started to return, his chest gently rising and falling as if he's just having a nap.

"Woah, that was—" Casey looks up at Shadow, frowning. "Hey, you okay?"

Shadow's body flickers like a TV with a bad satellite connection and he swears that she looks smaller than usual. She opens her eyes again, but only halfway, her shoulders sagging as she takes long, shallow breaths.

"Oh, I'm peachy," she says. "Sucking pure evil from a wound and taking it into my body is a total cakewalk."

"Hold up," he says, holding up a hand. "You took Raph's infection or whatever and now you have it in your own body?!"

"I can't get sick, and I can't exactly leave it floating in the air. It needed somewhere to go," she says. She rolls her shoulders and lets out a long sigh as she turns to the door. "I'm going to need to rest here. Ask the others not to bother me."

"Wait," Casey says. She stops and he comes closer. "Is Raph gonna be okay? And how did you know how to do that? Can you do that with other infections or—"

"You ask...a lot of questions, right at the worst time," she sighs. She yawns, her eyes disappearing for another brief second. "One, he'll be fine. Should wake up soon. Two...no, I can't do it with anything else, just injuries from other shadow mutants."

"And—"

"And..." she interrupts him, her expression neutral. "I know how to help because I've done it before."