The teens traverse the hallways at a steady pace, only occasionally stopping when they need to duck into hiding as a few droids pass them. Sarina is slower to notice when the Kraang are near, thanks to her helmet, and that only serves to put her on edge. After a while, their cautiousness starts to fade in wary confusion.

"This is too easy," Casey whispers.

"Don't get cocky," Leonardo warns. "Stay alert."

Raphael slows down as they pass a room, peering into the window with a frown. "This place is deserted," he says. He turns to face his team, his brow still furrowed. "Something's up."

The boys cast a quick glance to Sarina, but she's already looking at them. "Indeed," she agrees, grave. She starts walking again, urging them to follow her. "The Kraang have struggled with their plans for Earth recently, thanks to you. They've been packing up what they can and bringing it back to Dimension X for further study. They only come back to Earth for updates and gathering supplies." Her eyes flash and her jaw clenches. "I, too, was scheduled to be taken to Dimension X with any other outstanding experiments. That, of course, is when I escaped."

"So the Kraang are really gone? That's what you're saying?" Michelangelo asks, eyes brightening with excitement.

"In a sense," she answers. "I was far too consumed with the idea of escape to worry about the possibility of the Kraang actually following me. I assumed that they would forget about it, give up the chase. I don't know why I'm valuable enough to warrant being hunted down by them. One of the unsolved mysteries of my life, I suppose." Her eyes flash and she suddenly looks a lot softer, a lot more pitiable. "Oh...I was foolish. The one time in my life when I did not think, when I just needed to escape, and I brought about all of this...how stupid." She stops walking and does an abrupt about face, making the ninjas also halt. "I am truly sorry for everything. I promise to make it up to you somehow."

Her voice dies abruptly as they lapse into silence. She feels slightly warm in the cheeks upon realization of how much she just said. Yet, even with that information dangling in the air, she hopes that it will somehow help her regain their trust. Never has she wanted anyone to trust her so badly as she does now. Feeling that absence is like nothing she's felt before.

Leonardo startles in place and lifts his hand, tilting his head slightly as he listens. There's faint, clanking footsteps in the distance. A few seconds later, Sarina feels the faintest buzz against the base of her skull and she reaches to brush the helmet encasing her head.

"There's more than before," she utters, eyes flashing. "They must have come back for another shipment."

"Got a plan, Leo?" Raphael asks, immediately looking to his leader.

Leonardo's expression is set. "We should split up. One half goes and finds the medicine while the other distracts the Kraang."

"I'll take Mikey and Casey," Raphael offers, spinning one sai. "We'll take out the robot happy meals."

"Aw yeah! Best team ever!" Casey grins, fist-bumping Michelangelo and making an explosion noise. Raphael looks as if he suddenly regrets his choice of teammates.

"Then I've got Sarina and Donnie," Leonardo says with an assertive nod. "Sounds good. Ninjas, split."

They obey the order, the groups breaking off in separate directions. Leonardo, Donatello, and Sarina move as fast as they can, spurred by the sound of Kraang bots being destroyed behind them. Sarina leads the charge, keeping just slightly ahead of Leonardo so that she can peer into the rooms as they pass.

"Any one of these should have the medical stash inside. My mind map is a little fuzzy," she says, stopping to stare through yet another window. "With luck, they won't have cleared that out quite yet."

They continue on. Donatello and Leonardo glance at one another occasionally, silently questioning. Sarina appears, by every right, calm, but both turtles imagine that she's not exactly comfortable being back here.

"So...Sarina," Leonardo says, clearing his throat. "You said the Kraang tested and perfected this medicine on you when you were younger—"

She straightens and spins around to face them, eyes flashing once. Leonardo steps back with hands raised, her sharp glare piercing him straight through. If looks could kill...well, the leader in blue would be long gone.

"Maybe now's a bad time," Donatello suggests, stepping between his brother and the cyborg as he places a gentle hand on her shoulder.

"I have found that, as of late, I do not want to talk about it," she utters, her tone cold enough to make Leonardo shiver. Donatello removes his hand from her and flashes a hesitant smile.

As she turns, scanning the hallway, Leonardo nudges his brother and mutters under his breath, "I almost miss when we couldn't set her off."

"I heard that."

He bites his lip and shuts his eyes as he takes a deep breath. She's definitely spent some time with Destiny, he thinks.

She finishes her scan and nods briefly before continuing on. Donatello stays at her side, hands fidgeting at his sides as he tosses around questions in his head. He keeps thinking of his little chart back in his lab, dotted with blank squares, unanswered questions, wobbly connections, all mocking him in his lack of knowing.

"Sarina," he says, making her eyebrows lift in attentiveness. "I'm just wondering, but...you've mentioned this need you had to escape before. You knew escape was possible and despite being emotionless, unfeeling in every sense, you clung to this one belief." He shrugs his shoulders. "You never even witnessed an escape. It's shocking that you believed in it so fully."

"That last statement is not quite true," she replies. Her eyes flash and she purses her lips thoughtfully. "I witnessed an escape at some point, but the memory is very fuzzy. I can't remember many details. It was some mutation experiment that broke out, I believe."

"Like...giant animal?"

"Something like that. Like I said, I remember very little."

Donatello feels a slight jump in his chest and has to bite back a tiny smile. There's two theories buzzing around in his head now, but one is less likely. Leatherhead broke out of Kraang clutches, but he was mutated in Dimension X...not TCRI. His heart pounds even harder and he feels the desperate need to race home and get back to work.

Leonardo stares at his brother with slight concern. His excitement, to him, seems unwarranted and spontaneous.

Sarina stops again, doing another quick scan. Perking up, she strides to a door a little ways away on the left side of the hallway. She gestures to it, gazing expectantly at the turtles, and they hurry to catch up. Donatello peeks into the room, eyes widening as his mouth falls open. There's not much to look at in terms of variety, but the shelves lining the three visible walls within are packed with silvery metal boxes reaching floor to ceiling.

"Woah, that's a lot of medicine," he says.

"Make it quick. I don't want to be here any longer than we have to," Leonardo urges.

Sarina moves to the keypad and places her palm against it. Her eyes glow steadily and there's a few seconds of whirring before there's a satisfying click and the door slides opens with a soft swish. The trio sweeps inside without a sound and shuts the door behind them. While Sarina and Donatello start searching for the medicine, Leonardo watches the hall.

After a few minutes of sifting through boxes, Sarina lets out a happy gasp and plunges her hand into the box clutched in her arms. It reemerges clutching a transparent metal tube with a reddish-pink liquid inside.

"High-grade burn cream, infused with infection-killing antibiotics," she says with a proud smile as she puts the box back. "Sarina tested and approved."

Donatello laughs, fist-pumping the air for a second. "Yes! Let's go."

Leonardo nods and checks the hallway once more before opening the door. They head out, Donatello pulling out his t-phone to arrange a rendezvous point with the others while Sarina and Leonardo work together to find the way back.

They haven't walked far when Sarina stops dead in her tracks, her gaze fixating upon a new doorway. Inside, it's very similar to the medicine room except the walls are lined with Kraang-like filing cabinets.

"Sarina, what is it?" Donatello asks.

She doesn't respond, silently handing him the medicine as she walks to the keypad. She bypasses the lock and walks inside, prompting the turtles to follow her. Her eyes skim over the labels on each cabinet before stopping on one bearing the number "19-97-98". She opens the drawer to find five files, ranging from 60180 to 60184. Three of the five are thin and nearly empty save for a folder labelled "Early Stages"; the other two, 60182 and 60184, are thicker.

She instantly reaches for the one displaying her subject number. It's the biggest of the cluster, jam-packed with papers and reports of all kinds, documenting sixteen years of experimentation. She clutches the folder to her chest as if it's a treasure that'll be taken any second.

"Sarina, what is that?" Leonardo asks, finally pulling her out of her mind-scape.

She blinks and shakes her head. "My file," she answers. She moves robotically as she hands the precious package to Donatello. He takes it after slipping the medicine into his belt. "The Kraang take great care of their information," Sarina adds. "Paper copies and electronic copies are made whenever an experiment is carried out."

Donatello eyes the folder, but does not open it. Instead, he peers back into the drawer. "What are those others about?"

Sarina looks back into the drawer and checks them. "Experiments of Late 1997 to mid-1998. Objective: shifting beasts. 60180, female, blind...did not survive mutation. 60181, male, premature, died before mutation could occur," she reads. Three stomachs plummet in synch as Sarina's heart starts to beat a little faster. "60182, female, orphan, successful mutation into shifter. 60183, male, missing half an arm, did not survive mutation. 60184, female...successful cyborg-Kraang mutation, special circumstances." She chokes on the words, eyes starting to burn as she grips the edge of the drawer, looking away from the files. "Pardon my language, but...those bastards."

"I think the language is justified," Donatello whispers, his hands starting to shake.

Leonardo moves to Sarina's side, forehead creased. "What was that...Subject 60182, I think? She was the only other one that survived and she's right around our age," he says, reaching for the file. "It can't be..."

The file Leonardo holds is the only other one with more than a few sheets of paper inside, and when he opens it, he finds that this one is accompanied by a hefty portfolio labeled with a red stamp proclaiming "Discontinued".

"Why would they discontinue a perfectly successful mutation?" Sarina murmurs. "That is not like the Kraang."

Donatello's mouth goes dry. "Shifting beasts..." he croaks. "No..."

Leonardo opens the "Early Stages" folder and is immediately greeted with a picture. Within the white border is a baby girl with the faintest wisps of curly brown hair covering her tiny head. Judging by the fact that she's sitting up unassisted, she has to be at least six months old. She stares out from the page with wild green eyes, an unmistakable set of tiny little wolf ears and a tail poking out from her diaper making the identity of the baby glaringly obvious.

Leonardo nearly drops the photo as he slams the folder shut, handing it to Sarina with a thoroughly shaken look on his face. Sarina takes the folder, shocked, and Donatello immediately rests his hand against Leonardo's shoulder.

"Leo," he whispers. "Are you—"

"Destiny gets to read that first," Leonardo says, shaking his head as if to dislodge his scattered thoughts. "It...it belongs to her, after all."

"Definitely," Donatello agrees softly. He turns and hands Sarina's file back to her.

Sarina can't bring herself to speak, staring down at the precious documentation with bright, wondering eyes. A piece of paper starts to slip from Destiny's file and Sarina snatches it, tucking the folders beneath her arm as she glances at the page.

She immediately looks across the shelves, searching down the years for anything related to 2001. She shuts the open drawer just as she finds the label: "20-01-02". As if tugged by a magnet, she reaches up and opens that one too, finding one folder inside. It's easily twice as thick as Destiny's, but not anywhere near as stuffed as Sarina's.

Leonardo notices what she's doing, eye-ridge arching. "Sarina, what is it now?"

"I have a feeling..." she murmurs.

She opens the folder and sure enough, the first page is one loaded with general info about Subject 61390. There's a picture of a small boy with shaggy brown hair, eight years old at least, clipped to the info page. He stares emotionlessly at the camera with hollow, empty eyes, as if something has sucked the life out of him.

Sarina turns to her companions, holding the folder out to them. "I thought that Diaval seemed familiar to me."

Donatello is halfway between completely freaking out and completely geeking out, unable to think of anything else but his lab and that map. Leonardo, upon seeing the picture, shuts the file and gives it back to Sarina, shaking his head.

"The same goes for him that went for Destiny," he says. "No one reads it until they do."

Donatello and Sarina nod once. Donatello starts to speak, but the sound of gunshots from down the hall shatters his words as Sarina nearly drops the files. Leonardo gives a quick shout for them to run, and once they're back in the hallway, the piercing scream of Michelangelo reaches them as the turtle rounds the nearest corner.

"Dudes! Kraang! Lots! RUN!" he hollers.

Raphael and Casey appear right behind him with more than a dozen Kraang droids following them, guns blazing. Leonardo and Donatello whip out their weapons and Sarina clings to the folders even tighter.

"Kraang, the turtles have brought the one known as Subject 60184 to Kraang."

"We haven't brought you anything!" Raphael snaps. The Kraang keep shooting and Raphael ducks, allowing Leonardo to block the blasts with his katana.

The blue-masked turtle's jaw clenches. "Retreat!" he orders, already starting to back up. "Go!"

They turn and zip away down the tunnel, bullets ricocheting off the walls and nearly hitting them a few times. Donatello shoves the medicine deeper into his belt as they wind and twist through the hallways, gaining distance little by little but never getting far enough away from the Kraang to stop and figure out where they are.

After weaving down many halls, still being pursued relentlessly with no sign of the Kraang stopping, Sarina stops. She turns back the way they came, just able to hear the pounding footsteps of their enemies. The base of her skull tingles more and more the closer they get.

"Sarina, come on!" Donatello shouts as the others keep running.

She looks to him, her eyes sad. She pushes the folders into his arms and he looks from them to her swiftly. "Show them to Destiny," she says, a strange calm falling over her. "Whatever is in there, she deserves to know about it."

His expression flickers with fear and denial as realization hits him. "No," he insists. "I'm not leaving you here. You can show her yourself."

"The Kraang want me. That's all they're after. I'll hold them off, you'll escape with the medicine, you won't have to worry about being tracked. Besides," she says with another sad smile, "it's not like anyone in the lair wants or needs me."

"Sarina—"

"Donatello, please...trust me, one last time. You'll be okay."

The silence is suddenly far too loud and he can't get himself to breathe. There's so much he wants to say to her and now that time has been robbed from him. He wants to apologize. He wants to tell her that he does trust her and that he knows that she wouldn't turn on them, that he believes her. He wants to tell her that he really doesn't mind her questions and her misunderstandings, to tell her that he would miss her too much if she left now, but nothing comes out. The torrent of emotion has silenced him.

There's a crash from down the hall and as Sarina swivels around to face it, something knocks the complex ramblings from Donatello's throat and he finally speaks.

"Please," he says, reaching out to grab her wrist. "I want you. I...I need you."

Time slows. Sarina's bright, intelligent eyes meet his and she smiles just a little, then time speeds up again. She takes the helmet off and reaches up, slipping it over his head, and as it falls into place, she leans up and presses a soft kiss to his lips. She is suddenly the one thing that he didn't know he wanted until this moment. His entire body floods with tiny, buzzing sparks, his mind goes blank, and he has the insatiable urge to secure his hands around her waist and hold onto her for dear life, but she breaks away and her warmth disappears before three seconds has passed.

When his eyes open, she's running down the opposite hallway at full speed. Donatello stands frozen, trying to make himself go after her, and he feels a hand on his arm. He looks behind him and meets Raphael's distinct green stare.

"Move your shell! Come on!" he snaps, dragging his brother down the hallway and away from Sarina.

Donatello somehow makes his feet move, just able to hear the Kraang calling about "tracking down the subject" as he's thrown into the elevator after the others. The gunshots fade as the elevator starts its descent, everyone catching their breath, soft panting stirring the quiet.

Leonardo looks over the group and frowns. "Where's Sarina?" he asks.

Four pairs of eyes latch onto Donatello. The purple-masked turtle sinks to the floor of the elevator, dazed, his face red, his arms dangling limply around his legs with the files tucked safely against his plastron and the medicine still in his belt.

"She...she stayed back...led the Kraang away..." he mumbles, rubbing his forehead as he tries to come back to the present. Only when he does that does he remember that he's wearing the makeshift helmet, immediately making him choke up.

"What?" Casey demands.

"She was con...convinced..." Donatello gives his face another hard rubbing before he yanks the helmet off and throws it to the floor, mouth quivering. "She thought we'd want it this way, that we didn't...want her."

Michelangelo's shoulders slump. "She was never one of them, then? She was innocent?" he whispers.

In the resulting silence, Raphael is the first to break it. "We're going back to help her," he insists, guilt evident on his face. "We owe her that much."

"We can't," Leonardo says. He casts a quick glance to the files in Donatello's lap. "We need to get back to the lair and give Destiny the medicine."

"Oh, great! Then you can be the one to tell her that we purposely left her roommate behind!" Raphael snaps, jabbing his finger against his brother's plastron.

Leonardo slaps his hand away. "I will tell her!" he retorts. "I will tell her that without Sarina's help, we wouldn't have gotten the medicine and we wouldn't have gotten her TCRI file."

"File?" Casey asks.

"So you're choosing some paper over Sarina?" Raphael asks. "What kind of lea—"

"Don't you dare finish that sentence. Just because you feel guilty—"

"Guys, woah!" Michelangelo snaps, getting between the two of them and shoving them apart. "We all feel bad about what happened and fighting isn't going to help anything. She's still gone!" He gives each turtle a short, stern look that silences them from shock factor alone. Michelangelo softens just a little. "Sarina...I don't know what she was thinking, but she...she made her choice." He looks to Donatello. "Right, Donnie?"

Donatello hugs the folders and manages a weak nod just as the elevator dings and the doors slide open, letting in a square of moonlight. The purple-masked turtle gets to his feet and walks out in utter silence. Michelangelo stoops and picks up Sarina's helmet before departing.

Donatello stays mute when the group reaches the Shellraiser and stays that way the whole drive home. The only thing on his mind is Sarina and her goodbye kiss.