It was like sprinting miles down a black tunnel with dimensions specifically tailored to accommodate him and his katanas only. The air was thin and cold and made his chest tighten underneath his plastron and his skin bubble up with goosebumps and the tips of his fingers go numb with a loss of circulation. His eyes never adjusted to the black walls; he was aware of nothing outside of the tunnel and its mocking echoes of his tempered breathing and working pulse accept for the brilliantly white archway growing closer and closer but never near enough to reach out and touch.

After chasing her throughout half the city, his exhaustion had distorted into numbness—muscle memory. His body simply knew that it had to keep moving and so it did, bandaged feet silently pounding the ground at a speed no turtle had ever been witnessed traveling.

He wondered where she was going, if she was just leading him in angular circles to expend his muscles and strain his lungs until he eventually gave in and conceded to let her free … But he wasn't going to do that. He couldn't. The last time he had watched her disappear—becoming nothing more than another mysterious accessory in this estranged city, which was already bursting at the seams with oddities—he had not only placed an incomprehensible weight of shame on himself, but upon looking up to his father that night, he'd seen nothing but raw pain and disappointment.

He had failed to save Karai, failed to prevent her from being submerged in a vat of mutagen when he had been the only one close enough to stop it, failed to keep her from slipping away after the fact, failed to even stop her from leaving the lair in the first place—and this whole chain-reaction of disasters was what he'd seen reflected in his Sensei's eyes that night. Splinter had lost his daughter again and it was because of him—because of Leonardo's inability to handle the situation in such a way that a leader should be able to. He could not and would not return home empty-handed. He couldn't look his father in the eye and tell him that he had personally let Karai slip away again.

What he would do with her and how they'd get her back home once she was safely in his arms again, at the moment, was unimportant. There was no strategy on this one. His sole objective was to run and retrieve, and he would not allow himself to quit until this was accomplished.

He kept his blue eyes narrowed on her snowy scales, occasionally glistening with hues of purple and silver beneath the city lights. The muscles in his legs were burning but he pushed them to run faster, to be strong and unyielding. If he'd learned anything from eleven long years of ninjutsu training, it was that his body was always capable of more than it let on. However much it whined and ached and burned and hissed at him with contempt, there was always more for it to give, and he was always one to challenge it in giving more.

Despite the creeping exhaustion, he forced himself to breathe in a regular pattern—in through his nose, out through his mouth, slow, steady, concentrated, and not too deep. Of his brothers, he had been the first to fully grasp breathing techniques in such a way that kept his body fully rejuvenated, so that he could push himself longer. Of course, he was always the one that spent extra hours meditating with his sensei, being carefully studious of the master's every inhale and exhale, precisely executing his sensei's own techniques until he mastered them himself, practicing the complicated art of retaining a patient and controlled demeanor. He hadn't quite perfected it yet, but he was determined to achieve the same level of endurance that his father had, and he wasn't about to give that up now.

And so the distance between him and the bright white archway of the end of that tunnel continued to diminish. He was so close now that he could actually make out each individual scale rippling down her back. He gritted his teeth and reached out, his green skin illuminated by a white-yellow light that bounced off of her reptilian skin and flashed in his eyes. He heard the vague echo of something loud, hulking, and close, but it didn't matter, because Karai was mere inches from his fingertips now. One strong lunge and he would have her.

Just as he bent his knees to propel himself forward, he was rammed in the back with a crack of shell-on-shell that made his ears ring. Arms clamped around his torso, and his fingers just brushed the end of Karai's tail as he hit the ground with a breath-snatching impact and skimmed across the pavement with an extra weight on his shell that eventually pinned him to the sidewalk.

It was like being slapped out of a dream, only to realize that reality was much more forbidding and dark. The tunnel walls vanished and allowed a cacophony of noises and a multitude of shades to render him deaf and blind. There was a shell-rattling honk of a semi blazing by and shattering a Footbot to pieces, sending shards of metal in every direction. There was a war of man-made lights and shadows crossing paths along the entire block, illuminating the figure of Tigerclaw gliding overhead and obscuring the beam of white that had been the end of his tunnel. He watched with wide, burning blue eyes as the very tip of the same tail he'd just had his hand on disappeared into the shadows.

"Karai, no!"

He wasn't breathing regularly anymore. In fact, if his oxygen intake was cut any shorter he'd sure as pass out. He felt that dreaded failure instantly converge on him like a fleet of Footbots he was expected to ward off alone, and he immediately tried to run from it, pushing the weight off of his carapace and jumping to his feet. He bolted toward the alley down which both Karai and Tigerclaw had just vanished.

There was nothing there—mere shadows, a couple of rats, and a sickly dumpster that was hacking its contents onto the cement already plagued with bits of broken glass.

His throat caved in on itself and his head shook without permission.

"No."

The word passed his lips in a denying choke, barely making itself known even to him. He ran into the alley and searched every corner, grinding the glass underfoot and sending the rats scattering. He jumped up onto the fire escape and darted to the top, nearly tripping over the ledge of the building when he broke the surface. He turned in circles—the oxygen thin in his heaving chest—and saw nothing but dark, clear, unsuspecting rooftops.

"No … No!"

His body turned in aimless circles, nearly losing him his footing, then it jumped down into the alley again, landing in the infested dumpster. He began throwing trash around, peppering the alley with take-out boxes, and shredded papers, plastic bags, Styrofoam coffee cups, an old boot, a baby doll head, rotting fruits and un-namable objects that had gathered a coating of slime and dead flies. He didn't know what he was looking for, only that he wasn't finding it.

"Leo."

He heard his name, but it grazed off his eardrums like the wind on the back of his head.

A flare of anger set his chest alight and he rammed his foot at the side of the dumpster, sending an echo of vibrating metal throughout the alley. He jumped out and kicked it again and again, threw his fists at it, kneed it in the gut, throttled its rim with his hands as though it was an informant refusing to give him answers.

"No. No. No. NO!" he screamed, beating the helpless hunk of metal to a pulp, blowing permanent dents into its steel face the size of his fists.

He kicked it with his heel and it pushed him backward defiantly. He clenched his teeth, yanked out his katanas and sent a flashing silver bout of blades perforating down on the dumpster like a gale of lightning.

"Leo!"

He whipped around, casting out one arm with a lethal strike that cut itself short directly before Raphael's throat.

Leonardo glared down the length of his katana, paying no mind to the trembling of his arm or the sting in his eyes. His blood ran hot and fast through his veins and a film of red entered his vision.

"You," he hissed, his voice slithering down the metal of his blade and cutting his brother across the cheek in a venomous whisper.

His grip tightened on the handle of his sword, but all he could feel was the emptiness of his palm—where, if Raphael had not interfered, he would be holding Karai right now. There was something that he had been trained most of his life to do to those that got in the way of his objective, and his muscles now strained themselves with the temptation to unleash that training on his brother.

The red-banded turtle neither blinked nor lifted his chin away from his brother's threatening blade. "Leo—"

"I had her," he interrupted, arm shaking but voice steady. "I was this close!" he shouted, stepping forward, pressing the tip of his blade against his brother's skin. Raphael didn't flinch. "I had her!"

A ripple of predictable cheek flashed across Raph's eyes. "No you didn't. Your ass was half a second away from being flattened by a truck!"

"I could've brought her home, Raph!"

"Leo, you just screwed our entire mission! You said we were up here for mutagen and mutagen only. We could've come back for her. Now we don't even know where she is again, the damned Foot probably has her!"

"Because you pushed me out of the way—"

"I saved your shell, Leo—"

"You always screw things up!"

"Shut up! This is your fault, and you know it!"

Leonardo's katanas clattered to the ground as he chucked them aside. He took one threatening step forward.

"Leo! Raph!"

"Dudes! You guys are such epic jerks."

Leonardo hardly blinked at the approach of his brothers. He kept his eyes narrowed on Raph as his muscles solidified and resolved to keep stock still.

Raphael traded his reluctance to match Leo's glower with a shove against the older turtle's plastron before turning to shout at Donnie and Mikey. "Where the hell have you two been?"

The two younger turtles stopped at the mouth of the alleyway, panting and bruised. Donnie leaned carefully against the wall, presenting the splattered artwork of foreign blood staining his plastron. Mikey cradled the duffle bag of mutagen against his chest and twisted his freckled face into a look of scorn. Only it didn't work as flawlessly as he probably thought it did. Mikey normally couldn't pull off the I'm-totally-pissed-at-you-guys guise.

"Well, after you guys ditched us, Shredder's pet mutants tried to turtle-nap Donnie. I had to Chuck Norris their asses to save him." He swiped a thumb across his beak and sniffed smugly. "Because I'm awesome like that … But you two totally aren't."

Donnie didn't comment on Mikey's explanation. His brown eyes were watching Leo, who looked back at him with a glare. "What happened to Karai?" he asked cautiously, his brow furrowed with concern.

Leo's chest expanded dangerously and he didn't stop help himself from pushing Raphael to the side. "Raph let her get away, and Tigerclaw probably has her now."

He watched Raphael's jaw flutter, but his red-banded brother did not turn to face him. "Fearless almost got his shell crushed by a semi and is pissed because I pushed him out of the way."

"I would've been fine."

"Yeah. Fine as road-kill, Leo," Raph shot back, just barely shooting him a glare.

Leo snapped a sharp blue gaze at his brother and used his foot to fluidly sweep up one of his katanas into his palm. He aimed the tip back at his brother threateningly, stepping forward. "I didn't ask for your help, Raph," he said, voice rising to an echoing level.

"Whoa, Leo," Donnie said, limping over to calmly ease down the point of his brother's katana. "Look, I understand you're mad, but now's not the time for an argument. We need to get back to the lair and—"

"I'm not going back home without Karai!" he shouted, the very moment that Raph shoved Donnie's shoulder and exclaimed something about not needing his protection.

Though the jostle caused him to stumble forward a bit, Donatello ignored Raph and gazed at his older brother with pleading brown eyes. "Leo, we can come back for her," he reasoned. "If the Foot has her, then it's more imperative than ever that we finish the retro-mutagen so we can change her back. Otherwise they'll use her against us."

Leo gritted his teeth, his katana-wielding arm trembling again. He couldn't loosen his grip. He couldn't breathe steadily. He couldn't shake the sound of his own heartbeat pulsing in his ears. Donnie couldn't possibly expect him to wrap his mind around what he was saying.

A war waged beneath his skin, shaking his bones at the thought of returning home to explain to his sensei what happened, that he'd found Karai and yet stood before his father empty-handed. He felt like he was going to throw up.

He shot a glare over Donnie's shoulder at Raph who had his arms crossed in a silent fury, his glower cast to the side, jaw taut.

A fire burned in Leo's stomach.

"Leo," Donnie said, resting a gentle hand on his brother's rigid shoulder.

It was only out of stiff respect that Leonardo met Donatello's gaze.

"We'll get her back," said the sensible brother. "I promise. We need to go home; we got what we came for."

Leo's jaw rippled with strain. He squinted to the point of blindness to defend himself against the sting in his eyes. He could hear his shell creaking with indecision as he leaned in no particular direction. Voices were screaming in the back of his head.

This is all Raph's fault.

Go after Karai.

Donnie's right.

He closed his eyes, pried his teeth apart, then finally exhaled through his nose and swiped up his other katana, sheathing both weapons on his shell.

"Let's get out of here," he grumbled, walking past Donnie and Mikey and knocking shoulders with Raph.

He didn't meet his brother's scowl.