She pulled back the lab door as quietly as she could, but the metallic groan it gave still cut the air in half with the jarring sharpness of an alarm.

She paused, glancing over her shoulder toward Mikey who turned over sleepily on the bench and resumed snoring. April resituated herself on the floor of the pit and rested her head back against Mikey's shell once he was still. Her eyes were red and glossy with exhaustion, but still she fought off sleep as though it might steal her heartbeat from her. Instead, she stared blearily out across the lair at nothing in particular, holding her phone in one hand and Donnie's mask in the other.

Karai turned back to the lab door and squeezed her way through the small gap she'd managed to make.

The lab wasn't as thick in silence as the rest of the lair had been for the past couple of days. There was a humming presence of electricity moving through the lights and computer and whatever other machines Donatello had left unattended. And now a rhythmic thumping, accompanied by whispered chants that she couldn't quite make out yet, added to the ambiance as well.

For a moment, she stared across the room at Leo without moving any further, and just watched him as he sat behind Donnie's computer, bathed in white-blue light, repeatedly dropping his forehead on the desk. He had his hands over his head and his arms pinned close to his temples as though he was blocking out any excess noise. But the only audible disturbance that existed at the moment was coming from him.

She inched closer, silently, though she didn't think he'd acknowledge her even if he knew she was there. She tilted her head, straining to hear the words he was repeating to himself. She didn't catch it until she was standing directly over the opposite side of the desk.

"What would Donnie do? What would Donnie do? What would Donnie do?"

She stared and wondered whether or not she should interrupt him, seeing as he already seemed to be having a hard time focusing.

In the end, she found herself scooting around the desk to peer at the screen of the computer.

Scrawled across a virtual map in harsh red letters were the words: Signal Not Found.

Her eyes dropped, and she suddenly decided she didn't like the turtle's mumbling.

"I thought you told Mikey that tracking him would be a waste of time."

Leo's forehead fell onto the desk again, but for a second afterward he did not move. She watched him breathe and close his hands more securely around his head.

Waiting out the silence with him was even more uncomfortable than it had been when she was sitting with April and Mikey.

"I don't know what else to do," he whispered.

She released a long exhale through her nose and turned to push herself up on the edge of the desk. She clasped her hands together and stuffed them between her knees.

She didn't respond.

Eventually he lifted his head. His blue eyes were just as irritated and glossy as April's. But Karai knew he too was far from allowing himself even an ounce of sleep.

"There has to be something else," he said, shaking his head as he stared at the screen. "Karai, there's got to be a place we've missed, or maybe that you've forgotten about …"

"I told you everything I knew, Leo," she said. "It's been months since I've been with him. He could've easily found a new place to hide by now."

Leo's chest inflated. "Then we'll have to look everywhere."

"We have been looking everywhere. It's a big city, Leo. He may have even left it by now, gone somewhere up state or out of it."

Leo's eyes tightened. "Don't tell me that."

"I'm just trying to be realistic. It's a possibility. And if that was the case then—"

"Donnie's screwed."

The harsh matter-of-factness in his voice surprised her. It even gave off a bitter echo of defeat, as though he was staring into his brother's future and witnessing the imminent end it was going to meet.

She didn't say anything, so they sat in silence again.

She wasn't quite sure why she'd come into the lab. Maybe originally she'd wanted to encourage him somehow, help him keep his hopes up, which was a weird thing to think. She'd never been that kind of person. But there had always been something about Leo and his determination that fed her assurances, that kept her, in a way, optimistic about the choices she had in life. Maybe she'd just wanted to return that favor … Except, so far, she was doing a terrible job.

She pulled in a breath and swung her feet. "So, what would Donnie do?"

He shook his head. "I wish I knew. I wish I didn't even have to ask myself … I can't do this without him."

"But you have to."

He grimaced and let his head tilt forward in his hands, hiding his face. "You don't understand."

The very corner of her mouth became slanted, but she decided not to challenge him. Opponents were no fun when they didn't have the motivation.

She pulled in another breath and finally tugged her eyes away from him, staring instead at that frozen jar of whatever it was standing against the back wall. She'd have to ask them about that one day.

She crossed one leg over the other and leaned back on her palm. Maybe silence was just the best way to handle this whole ordeal. That's what they'd all been doing so far. She couldn't say it was working exactly—it definitely wouldn't bring Donnie back—but at least it was better than the bickering they'd been entrenched in before the scrawny turtle's disappearance.

Then again, the silence might very well have been attributed to Raphael's current absence. And she couldn't say she wasn't grateful for that. Since he and Jones had gone off on their own to continue the search an hour ago, she'd found it ten times easier to breathe.

"I don't understand," Leo said suddenly.

She blinked down at him. "You don't understand what?"

"You."

"Me?"

He stared, his blue eyes steady and chilling. They looked rather dead in spirit—certainly not something she was used to—and she couldn't exactly say that made her comfortable.

She shifted. "What about me?"

"What does all of this mean to you?"

She raised a brow and let her eyes glance around as she thought up an answer. She was fairly sure she knew what he was implying, but she decided playing coy had always been a useful tactic for her.

She shrugged. "It means that the Shredder has your brother and—"

"That's not what I'm talking about."

She met his gaze again, and his eyes narrowed, challenging her to the try the truth for once.

She pursed her lips. "What are you talking about?"

"I think you know."

She rolled her head back, looking up toward the ceiling and exhaled heavily.

"You were my first friend, Leo. And for a while you were the only person to ever make me feel like I actually had a choice, like I could do something better with myself. And obviously without you I wouldn't be sitting here so …" She turned her eyes back on him. "You're important."

His eyes tightened at the corners with dissatisfaction. "Are you reciting words you think I want to hear, or do you actually mean it?"

Her shoulders dropped. She had to strain her expression to keep any defensive scowls out of it. "I thought you knew me better than that."

"Yeah, so did I."

They held a staring match for a moment, and she didn't expect to falter. Usually she was so good at holding her ground, especially in front of him. But it seemed a high-strung Leo was also a very fierce one. The best she could do was narrow her gaze before looking away and repeating, "You're important."

"What does that mean?"

She clenched her teeth and stared down at her feet. "It means … you're important."

"To who?" he shot back. "To you?"

"I don't think now's the best time for this conversation—"

"What does it mean, Karai?"

"It means you're my best friend."

She looked back at him, though she knew it would mean facing a pain she'd promised herself she wouldn't force him to endure again. But she had to, because he needed to understand. She could only be so much for him, and what she was already amounted to more than what she was willing to be for anyone else.

For a while, he just stared back, trying his hardest to stay firm, stay cold. But beneath that shell, that wasn't who he was. They both knew that. And she managed to catch a glimpse of his grimace before he looked away and tightened his fist.

They sat in silence again, and she finally began to resent it. At least when there was bickering she knew how to respond, knew how to hold her own and fight back. With the silence there was nothing to attack, nothing to hit, nothing to smirk at. It was just uncomfortable.

She curled her fingers around the edge of the desk. "I'm sorry, Leo," she said, directing her voice toward the floor. "I have nothing else to give you."

Though she didn't look directly at him, she could see his head lift through her peripheral vision. He stared at the monitor, and there was a lift in pressure as he opened his mouth to respond. But instead of words, the startling jingle of a ringtone dislodged the silence.

Leo's hand was a blur.

He snatched up his T-phone immediately, and Karai allowed herself to look back at him as he put it up to his ear, his eyes suddenly wide and alert.

"Casey?" The word came out as a breathless question, and it was layered with a pleading that Karai wasn't sure she wanted to hear.

She watched him as he listened, his blue eyes following Casey's response as though it had popped up in typed letters on the screen of the monitor. She could swear, for a moment, she actually saw his heart beating.

He stood, nearly knocking his chair to the floor as he did so. Karai's eyes traveled down his arm where he'd planted a palm on the desk. His elbow was shaking.

"Yeah? Okay … How many … No, don't go anywhere. We'll meet you there. Let us know if they move … Okay."

He stuffed the phone in his belt and immediately began trotting toward the lab door, scooping up his katana from where he'd left them leaning against the lab table.

Karai jumped down from the desk and followed. "What is it?"

"Casey and Raph spotted some Footbots heading east out of Little Italy. They followed them to an old warehouse on the Lower East Side."

Karai jogged to catch up with him as he noisily pushed his way out of the lab and headed straight for the turnstiles. He hardly broke his pace when he shot a glance toward the pit.

"Get up. We're on the move."

April bolted up immediately, wobbling a little when she shot to her feet. She shook Mikey's shoulder.

He popped out of his sleep with a squeal and fell in a heap on the floor.

"Wh-What? Shredder? Where is he? I got 'im." He stumbled to his feet, eyes half closed, and raised his empty fists as though his nunchucks were nestled in his hands.

"In a minute, Mikey," April said, latching onto his shell and pulling him out of the pit.

They all piled into the Shellraiser, Leo waiting to enter last.

Once Mikey had crossed the threshold, Leo stepped in but was stopped from going any further by a hand that rested itself on his shoulder.

Karai peeked out at her rat father who gazed at his eldest son with a crease of anxiety to his brow. "Be careful, my son."

Leo gave his sensei a resolute nod. "We'll call you if we find anything."

Splinter's whiskers twitched, and his pause could've been interpreted as hesitation. But he stepped back, folding his hands behind him and stared anxiously at the four of them until the doors closed on his gaze.

Karai's stomach turned, though she didn't know with what, so she ignored it.

She sat herself in Raph's seat then glanced up at Leo who jerked the throttle forward and hardly flinched when the Shellraiser jolted into action.