In Peter's bookcase, behind several significantly less dusty books, there's a wooden box with a triskele carved into the top. It's the kind of thing Mom would use—would have used—to hold jewelry. Derek can't imagine what it might be doing here, but he's done learning about his life from other people. He picks it up, opens it gingerly.

At first he's not sure what he's looking at, and then—

"Be careful with that," Peter says from behind him. Derek jerks to life, barely resisting the instinct to do a panicked spin. The claws leap from the box and scatter across the floor.

Derek sets the box down carefully and slowly turns to face Peter, expression as blank as possible.

"Your hands are shaking," Peter points out. Derek can just bet Peter's been watching him explore all this time and was just waiting for the perfect moment to scare the crap out of him.

He really hasn't changed at all.

"No shit," Derek says evenly. "Any reason you're keeping someone's claws in a box behind A Study In Being A Dick?" Something horrifying occurs to him. "Are they Malia's?"

But they can't be. Derek saw her claws, saw what was left. They were ragged, destroyed. These are whole, practically perfect, just the faintest smell of ash.

"They're totems," Peter says, but Derek's already scrambling to gather them, put them back.

They're not just totems.

"They're Mom's," Derek says. He counts the claws, spills them back into the box carefully, and closes the lid. He can't believe he didn't know immediately, but—Mom is still more than claws to him. He's still got this desperate, stubborn idea that she's alive, somewhere. Or at least whole, or at least…

His hands are shaking. He shoves them behind his back, fixes his face as stolid as he can.

"You're hiding my mother's claws," Derek says, somehow. "Why?"

"I don't need to tell you," Peter starts, in the tones of someone introducing a twelve part lecture, "that these aren't just claws. They're immensely powerful—"

"I know," Derek interrupts.

"So you know what could happen if they end up in the wrong… hands."

Derek rolls his eyes so hard he can practically hear Laura warning him they'll heal that way.

"I found them in two minutes," he says.

"I wasn't hiding them from you," Peter says. "They're yours now, after all."

Derek struggles to fight the sudden burning behind his eyes.

He doesn't want claws. He wants his mother.

"I know you want your mother back," Peter says kindly, or as close to kind as he can get. His version of empathy is worse than his patronizing speeches or smug judgment. It's like watching a snake try to emote. "We both want this to work. And those claws are the first step toward what we want."

"That's how you're going to do it?" Derek asks. "Plant them in a little pot, water twice a day?"

Peter looks irritated. It's a lot less eerie than his attempts at sincerity. "The Aztecs—"

"Right," Derek says. "Sprinkle with divine energy. Keep near sunlight."

"How do you think I came back?" Peter asks. "A totem, an anchor, and an energy source. The Aztecs may have been primitive, but in this case... they were right."

"So your totem was—"

"My body, of course," Peter says. "My anchor was—"

"Lydia," Derek realizes.

"You're not as painfully slow as you look," Peter says approvingly.

"And the energy source?" Derek says, nearly managing to ignore the jab.

"Kate Argent," Peter says.

"But you haunted Lydia," Derek says. "You made her do things for you. Is Dad—"

"Those were… unfortunate complications," Peter says. "Kate was supposed to die. Somehow, she didn't. She wasn't completely dead, so I wasn't completely alive. That won't happen again."

"The energy source is murder," Derek realizes. "The Aztecs believed in human sacrifice. Is that—"

"Murder?" Peter scoffs. "You had Kate Argent destroyed. Was that murder?"

"She was killing people," Derek says uncomfortably. "She wouldn't have stopped."

"Exactly," Peter says softly. "You and I, Derek, we're survivors. We do what has to be done."

"So Dad," Derek says, sudden dread creeping in. "Who's going to die so he can come back?"

"The Benefactor, of course," Peter says.

Mr. Tate killed people, Derek thinks, walking aimlessly. He killed kids. And no one can do anything about it because they're all animal attacks. And if killing him will bring Dad back—

But he's Malia's father. Derek's already taken everything else from her. He can't take this too.

Unless he can prove Mr. Tate is still dangerous. If he still hates supernaturals, if he still wants them all dead, then killing him isn't selfish at all. It's survival.

We do what has to be done.

Derek should've waited to kill Kate. He should've—but he couldn't have seen this coming.

Could he?

The fact is, Mr. Tate killed a baby. He killed a baby in a little wolf hat, and he said she deserved it. He called Cora—

Derek stops walking.

All this time his head has been spinning. He's been thinking he's alone, trapped, forced to trust his sister's killer. He completely forgot his other sister. His living sister.

He digs through his pockets, comes up empty. Of course. His phone is probably at the McCall's, with whatever's left of his clothes from that night. It probably didn't even survive. He almost didn't, and he's not a fragile slice of glass and plastic.

He should've memorized Cora's number. She programmed herself as his first contact, and he got lazy and didn't bother learning her number, and now—

She could be anywhere. She could be dead, or dying, and Derek would be more than useless, not even able to tell by the snap of pack bond because he isn't pack. He isn't her pack and all he had was a stupid human phone and he didn't think—

He has to find it. He has to find it, whatever's left of it, maybe there's a way. Maybe he can get it fixed, or get the brain of it put in a new shell, or—something.

There has to be something he can do.

The McCall house is silent when Derek gets to it. All those weeks of following Stiles like a lost puppy have one benefit, at least: Derek has inadvertently memorized Scott's schedule. In fact, he knows Melissa's shifts for the next three weeks, and he knows when Stiles' father will be coming and going too. The only unknown variable is Stiles. He has no reason to be at the McCall's when neither of them are home, but Stiles defies reason, and Derek knows he has a key.

But that's okay. That's okay. Derek can handle whatever the real Stiles has to throw at him, even if it shatters his stupid fantasy. He's not a kid anymore. He's not even really a teenager, though he keeps forgetting that. He can handle Stiles.

Probably.

Anyway, Stiles isn't gonna kill him, and if he does—

Then fine. Fine. Let him kill Derek, let Peter kill him, let the whole world go Douglas Adams style, whatever. What's so great about any of it anyway?

Sufficiently Kübler-Rossed, Derek scrapes a claw under the window latch until something gives.

It's Melissa's bedroom.

Derek feels a sudden sense of wrong so sharp it's laughable. He's not hurting anyone. He's not even taking anything that isn't his. But it's Melissa's bedroom, and she's never been anything but nice.

Like you'd know, some awful part of his mind laughs.

Derek grits his teeth, pushes her away, and clambers down from the windowsill without disturbing anything.

He tries to look for blood, for signs of himself, but once out of Melissa's room, he's overwhelmed by Stiles. He's everywhere, on everything. Derek's wolf is frantic, keeps turning him around, trying to find the place where the scent is strongest and settle there. Fighting it turns Derek into a dog chasing his own tail, and it's so stupid. Derek's so fucking stupid. Why couldn't he just tell Malia to keep him? Then Peter could bring Dad back, and Stiles wouldn't even be on Derek's radar anymore.

Lie, lie, Derek's the worst liar in the world. Maybe that's why he keeps missing it in everyone else. He's lie-impaired, so he keeps falling in love with sociopaths, and sooner or later one of them is going to kill him. There's no point being angry about it. Derek's anger burned out a long time ago. Maybe even longer than that.

He searches for longer than he can stand before stumbling out into open air, breathing and breathing and breathing.

Even Kate didn't make his head spin like this. She was never his anchor. But he and Stiles never even really kissed. Outside Derek's head, there wasn't anything but Derek's dumb move and Stiles stopping him, pulling away. It doesn't make any sense, except it still does, in some part of him. In some part of him, Stiles is still home, and pack, and the only right thing in the world.

Fucking instinct.

When Derek gets back, Peter is death-pale and sprawled in the doorway, clutching his heart as black blood streams between his fingers.