With a noisy splash, Leo and his brothers clambered up out of the sewer pond and into the lair.

"Okay," Leo said. It was the first thing he'd said since they escaped. "Is everyone all right?"

"Are you kidding?" Raph said. "Look at us! Look at you!"

Leo's hands looked like a gore fest – the water thinned out the blood and created the illusion that there was twice as much. The cut on Mikey's face also looked far more spectacular than it actually was. Raph didn't appear to be bleeding anywhere, but ugly bruises were raised all over his body.

"I can't believe that Karai's defective," Mikey said, with a little sniffle. "I mean, I thought she was our friend."

"Defected, Mikey," Leo said. "And there's actually a chance that she's still on our side – "

"Do you even hear yourself?" Raph yelled. "She gassed us, tied us up, and was going to kill us! How can any of that be considered 'on our side'?"

"What is going on out here?" Splinter emerged from the dojo. He looked at them, and his whole face shifted into an expression of horror. "What happened? Where is Miwa?"

"I'll tell you what happened, Sensei," Raph said. "Karai stabbed us in the back. She's actually working for Ronin."

Splinter blinked. He opened his mouth as if to say something, then closed it again. He looked at Leo, raising his eyebrows in question.

"That's certainly what it looks like," Leo said. He sighed. "She gassed us as we were going in – "

"You came in through the water with those injuries?" Splinter said, as if he had just noticed this.

Leo was taken aback. "Well, yeah, I was leaving a trail, and we didn't want them to be able to follow – "

"Come. We need to get those cleaned and treated immediately. I do not want them to get infected. Now, tell me the rest of the story."

All of them went to Donnie's lab. Splinter rifled through the medical supplies, not saying anything as Leo – frequently interrupted by Raphael – tried to explain what had happened.

Occasionally nodding, Splinter poured hydrogen peroxide over their cuts and treated them with antibacterial gel. "Yours does not need stitches, Michelangelo. Leonardo…how did this happen? Did you try to stop the blade with your hands?"

Leo cringed. "Mmyeah."

"What?"

"Hai, Sensei."

Splinter sighed. "The last time we tried that, I still landed the hit and you got splinters from the bokken. It was a foolish decision to try this in actual combat."

"Really?" Raphael said. "After everything we just told you, that's the foolish decision you want to point out?"

"Raphael! Be silent."

Still fuming, Raphael pressed his lips together.

Splinter turned his attention back to Leo. "You need sutures." He walked over to the medical supplies and dug around until he found what he was looking for. Then he came back, opened the sterile packaging, and started to stitch the wound. He had to keep blotting it with gauze because of the bleeding.

"I didn't have much of a choice, Sensei," Leo said, feeling more and more foolish all the time. Raphael was right, after all. The poor decision to stop the blade with his hands paled in comparison to his decision to ignore Raphael and trust Karai. "It was my first instinct. You're always telling us to trust our instincts…"

"Yeah, well, you should've trusted mine, too," Raphael quipped.

Splinter said nothing this time. He continued to focus on the wound.

"Leo," Mikey said, "do you really think there's a chance Karai's not defective?"

"A small one," Leo answered, not bothering to correct Mikey this time.

"Oh?" Splinter said.

"Yeah. Well, she said she was doing it to prove herself to Ronin, to show her loyalty, and then she looked right at me."

"She also said we were gullible idiots," Raph said.

Unfortunately, she hadn't been wrong. Leo's face prickled with heat at the thought. "Anyway, she also told Ronin it would take eight weeks for the Krang to develop the technology – but we all know the Kraang can move faster than that. There's a chance she's gaming him."

"Yeah, him and us."

"Raphael," Splinter said, "I understand your anger. But we must not make premature assumptions."

"What? Are you serious? She was going to kill us!"

"Yeah, but did you notice how easy to cut the cords were?" Leo said. "And why would Mikey still have a smoke bomb?"

"Probably because Karai didn't want to dig around in his shell for it," Raph said. "I can't blame her there."

Master Splinter finished the sutures, placed gauze over the cuts, and wrapped them tightly with medical tape. "You should both take antibiotics, as a precautionary measure. I still think we have plenty of the ones that Donatello made. Now – you mentioned that the Ronin wants Kraang technology? What does he want it to do?"

Leo hesitated. "He wants it – he wants to be able to sweep the globe to find anyone related to the Hamato clan in any way, so that he can kill all of them."

Splinter shook his head. "He truly is a madman. He must be stopped. If Miwa – Karai – has indeed joined forces with him…" His voice wavered. He drew a deep breath before continuing. "Then we must not let this plan succeed."

"You guys forgot your weapons," said a feminine voice from the lab door.

All four of them wheeled around. Karai stood in the doorway, holding a large bag. When she dropped it on the floor, it gave off a metallic clatter.

"You have some nerve – " Raphael started.

Karai put her hands on her hips. "Look, I know what you're thinking. I'm not on Ronin's side. I just had to – "

"Prove your loyalty to him?" Leo said, boiling with anger at the sight of her. He walked over to her. "What about your loyalty to us? You betrayed us!"

"It had to be convincing," Karai said. "A man like Oroku Daiki would be able to tell if you were acting."

"So you're saying that you're perfectly capable of acting, but we aren't? You should have told us!"

"Oh, please, like you would have gone along with it."

"Yeah, because it was too risky. You had no right to risk my brother's lives like that. None."

"But it worked. Ronin trusts me now. He – "

"I hope it was worth it," Leo said. "I hope his trust was worth it, because you lost ours. All of it."

"You know it was worth it. How am I supposed to work with him if he thinks I'm a liability? If I can't stay with the Foot, I can't work with the Kraang, and we can't find a solution for Donnie. How is that not worth it?"

Leo's temper abated slightly. There was something of a cold logic to it. "Well, yeah? Maybe your plan worked, and maybe it didn't. But I'll tell you what did work. You wanted the betrayal to be real so that Ronin wouldn't be suspicious? Well, it was real. More real than you realize. You betrayed me, you betrayed Raph, you betrayed Mikey. You put my brothers in danger. That betrayal was real, and it's not going to go anywhere."

Karai bit her lip and blinked several times. Her eyes were shiny, but there were no tears.

Not that tears would have meant a single thing to Leo now.

"I did what I had to do," Karai said. "Ronin is flying back to Japan this afternoon. He won't be bothering us for eight weeks, which gives the Kraang plenty of time to work on the retro-retro-mutagen. Mei will be out of the wheelchair by then, and she can be doubly sure that all traces of information about the lair's coordinates are wiped from the Foot's systems. Then we can all go underground."

"Oh, so you're not going to tell the Kraang that they need to make genocidal technology?" Raph said. "You're not going to put Splinter's head in the freezer?"

Splinter raised his eyebrows.

"After all," Raphael continued, "it would help convince the Ronin that you're really on his side."

"Of course I'm not. Ronin is a disgusting excuse for a human being. You've got to believe me."

"Yeah, well, the last time I believed you, that didn't go so well. The last time Aunt Mei believed you, that didn't go so well either, did it?"

Karai drew a short, sharp breath and squeezed her eyes shut. Then she wheeled around and left the room.

With a sigh, Splinter went after her.

Leo didn't know whether he felt sorry for her or not.

"Dude, that was a bit harsh, don't you think?" Mikey said.

"Are you crazy, Mikey?" Raph threw his hands up in the air. "Did you like, miss today or something?"

"I believe her. She said she did it for Donnie. I'm okay with that."

"Mikey, she put us all in terrible danger and didn't even tell us she was going to do it," Leo said. He folded his arms. She hurt you.

His heart twinged.

She hurt me.

"But like she said, it had to be convincing and stuff. You 'member that year we made Raph that bangin' mutation day present? I blew the secret the minute we'd finished. You know how awful I am at keeping secrets. I woulda screwed this up, big time."

"Then she could have at least told me and Raph."

"But you and Raph wouldn't have done it."

"Exactly," Raph said. "Because we're not crazy! It's a miracle that we even got out of there alive."

"Come on, Leo. Karai's your friend! You've gotta believe her, right?"

Leo sighed. He put a hand on his forehead. "I believe her. But that doesn't mean I trust her." Never again. "She's proven that she doesn't care about our safety."

Mikey hung his head. "I just – she's…" He looked up. "I trust her." He jumped up from where he was sitting and ran out of the lab.

Leo shook his head and looked at Raph. "I guess that's Mikey for you. Raph, I'm really sorry."

"Didn't hear that – what?"

"I'm sorry."

"Huh?"

"I. Am. Sorry."

"Oh, you're sorry."

"Yes. I should have listened to you. I just – I wanted to trust her so badly, and I thought that after she joined us, that…things would be different."

"Do you feel completely and totally miserable about this?"

"Yeah. Yeah, I do."

"In that case, we're good. Just stop being an idiot over her. Even if she wasn't totally evil, she's our sister."

Leo poked at the bandages on his hand. "You noticed that, huh?"

"Oh no, no, it wasn't noticeable at all. Are you kidding me? You act like a lost puppy around her. You put Donnie to shame."

"I'm an idiot, aren't I?"

"Yeah, you kinda are."

Leo started walking out of the lab.

"Where are you going?" asked Raph.

"My room."

All he wanted was to be alone.

Karai stood in the dojo, looking at the picture that Splinter had on his mantelpiece.

I don't belong anywhere.

She'd belonged, once. She had belonged perfectly with Hamato Yoshi and Tang Shen. When she was taken from them, and raised by the Shredder, she belonged perfectly with him.

Now, she belonged nowhere.

She thought that maybe she was starting to find a place in her new – old – family, but clearly, she had shattered that. None of them would want anything to do with her now. Even though she had done it for them. She had done everything in her power to make sure that they'd have a fighting chance at escaping. The cords were tight enough to keep them restrained, but the material wasn't very resistant against being cut. She'd made sure that they had a smoke bomb to get away. She'd even faked being knocked unconscious so that Leonardo would have time to free himself.

But none of that counted, because she really truly had betrayed their trust. Even if she'd done it for a good reason, she'd betrayed them.

And Leo…

He'd been her friend from the first, and she'd ruined that. He'd accepted her unconditionally all this time, and this was what had broken their trust? She thought for sure that he'd see it from her point of view when she explained it. After all, he had let go all of her past transgressions. What made this so different?

This time, he'd really trusted her. He never had before, and all of those offers of friendship were despite his distrust. Now that he really had trust, her violating it was a much greater sin.

Now none of them would forgive her.

Good. She understood grudges.

And yet…

The thought of them all hating her made her want to vomit. Tears started to well in her eyes – real tears, this time.

"Karai?"

Immediately, she blinked the tears away. In a moment, they were gone. She turned around to see Splinter standing a little way behind her.

"Don't worry, Master Splinter. I'll be leaving soon."

Splinter shook his head. "I do not want you to leave, my daughter. I understand why you did what you did."

"You do?"

"Yes." Splinter frowned. "This is not to say that I approve of it."

"You must hate me."

"No. I love you, Karai. I have always loved you, and I always will. But surely you understand how difficult it is for us to trust you now."

Karai nodded. "I don't belong here, do I?"

"There is always a place for you with me, my daughter. Come here." Splinter extended his arms.

Karai ran into them and buried her face in his chest. His arms wrapped tightly around her, surrounding her with unconditional love – the love of a father for his daughter, a love as inviolable as the law of gravity.

"We will find a way past this," Splinter said, in a voice that was calm and soothing.

And despite everything, despite the emotional turmoil inside of her, despite the anger and distrust she had caused, she believed him.