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When Stiles gets the text from Derek—come over now and don’t bring Scott—he tries to keep from panicking too hard over it. Derek would probably say so if something were actually seriously wrong. It’s not like there’s a mutated platypus-person with barbs on its tail running around Beacon Hills stabbing people in the ankles in revenge for being late on filing their taxes—
Okay, Derek really needs to start elucidating more, because whatever the problem is it could not possibly be more terrifying than the things Stiles’ brain is inventing to fill the gaps.
“What is it now,” Stiles says, bursting into Derek’s by-now-upsettingly-familiar train car. “And there had better not be any blood or bile this time or so help me—”
Stiles stops, and stares, and then blinks and stares some more. He was expecting something scary, or gross, or both, and so nothing prepared him for the sight of the cutest curly-headed toddler in the entire world sitting right there on the ratty couch Derek dragged home a few weeks ago, wrapped up in Derek’s jacket. He looks up at Stiles with huge, glowing, wary eyes, and Stiles lets out a completely involuntary cooing sound.
The tiny werewolf growls at him, which just makes Stiles want to tickle it, awwww. “Who’s the cutest little wolf baby, you are, yes you are!” he says, grinning when the little guy’s fangs come out. “Oh man, look at you, can I bop your nose? Can I?”
“Stop that,” says Derek. He’s leaning against the far wall with a backpack clutched tightly in one hand. “It’s undignified.”
“Aw come on,” Stiles scoffs, making funny faces at the kid to see if it makes him less grumpy. It doesn’t. “He’s so adorable it’s actually kind of ridiculous.”
“He's Isaac,” Derek says, and oh, right. That’s actually obvious now that Stiles is looking for it; those cheekbones are unmistakable. “And I don’t think he likes being called adorable.”
Stiles laughs. “But he is.” It’s really kind of an incontrovertible fact.
“Yeah, I know,” Derek sighs, his mouth quirking up. “Just try to ignore it.”
“DEREK,” Isaac commands, reaching grabby hands out from under Derek’s jacket and keeping a distrustful eye on Stiles. “Juice.”
“Yeah,” Derek says, and he pulls a juice box out of the backpack and punches the straw in. “What do we say.”
“Please. Thank you. Give me,” says Isaac, snatching it from Derek’s hand and smiling hugely when Derek—grouchy, standoffish Derek—actually reaches down to ruffle his curls.
“Oh my god,” Stiles breathes. “That was the weirdest and greatest thing I’ve ever seen.”
Derek looks vaguely embarrassed. “I found him wandering around like this.” He moves to stand behind Isaac, curling over him protectively in a way that he probably thinks is subtle. “He won’t tell me how it happened, though. Or maybe he can’t.”
“Yeah, I mean, toddler brain,” Stiles points out. “Isaac’s clearly still in there, anyway.” He sticks his tongue out at Tiny Isaac and gets a low warning growl for his trouble. “Though full-sized Isaac was never quite this upfront about his disdain.”
“He doesn’t disdain you,” Derek says, rolling his eyes. “He just doesn’t trust you. He’ll do what you say if I tell him to, though.”
“What?” Stiles glances at the backpack again when Derek comes out from behind the couch and holds it out to him. He looks inside and sees three more juice boxes, a toothbrush with a little cap on it, Isaac’s school books, and one of Derek’s softer-looking shirts. “Whoa dude, no way,” he says, backing up. “No. I’m not taking him!”
“Stiles. It’s just for tonight. I think I have a trail on whatever did this to him, but I need to start tonight before it goes cold.” He shoves the bag into Stiles’ hands.
“Derek, come on, I don’t—”
“He’s already eaten dinner. Give him my shirt to sleep in; it seems to make him more comfortable when he can smell me.” Derek sounds so disarmingly warm when he says that last part. Stiles feels his resolve crumbling already.
“Come on, Derek, why me. Why can’t Scott do it. Isaac likes Scott.”
“Scott?!” says Isaac, ears perking up. “Where?”
“I can’t trust Scott not to go to the Argents or Deaton over this. He’ll think it’s the right thing, and he won’t—”
“It won’t occur to him that he’s advertising Isaac’s vulnerable position,” Stiles finishes. “And by extension, yours.” It’s a legitimate concern. The alpha pack has been sniffing around for weeks now, watching and waiting, and Isaac is the only real pack Derek has left—except for Peter, of course, but Stiles tries hard to forget that Peter even exists.
“But it's occurred to you,” Derek says, giving him that faint Proud Alpha smile that he gives the betas sometimes. Stiles tries not to preen, because it’s not like Derek’s approval means anything to him. “It’s just for one night, Stiles. I'll pick him up in the morning.”
Stiles heaves a giant, defeated sigh and grabs the backpack out of Derek’s hands. “You’re so lucky my dad won’t be home until dawn. Come on, Mini Isaac.” He holds out his hand, and Isaac—looking about as bitter and betrayed as a three-year-old can possibly look—jumps down from the couch and takes it after Derek gives him a gentle shove. “Now,” says Stiles, raising his eyebrows at Derek, “what do we say?”
Derek snorts. “Please,” he says. “And thank you.”
*
“I want Scott,” Isaac whines, not for the first time. He’s curled up on Stiles’ bed, absolutely swimming in Derek’s grey henley. Stiles has given him Derek’s jacket to clutch like a security blanket, and he keeps burying his face in the leather like he needs it to breathe. “Your room smells.”
Stiles is at his desk, researching possible de-aging spells and resigning himself to not getting any sleep, ever. “It does not. Or at least, I’m sure it doesn’t smell any worse than Scott’s does. I’m not even sure Scott washes his socks.”
“Scott does too smell better,” Isaac says. He rolls over on his stomach and stretches out with his head down at the foot of the bed, so he can glare at Stiles. He bunches the jacket up and puts his head on it like a pillow. “Derek said he doesn’t but he does.”
“Is that right,” Stiles says, absently. It’s already past eleven, so he’s hoping that he’ll only have to humor Tiny Isaac for another ten minutes or so before he collapses in exhaustion.
“Yeah and Derek said he likes you and we trust you, and I have to listen to you or else.” Isaac wrinkles his nose. “Your heart goes too fast, I don’t like it.”
“Did you just say Derek likes me?” Stiles winces when his voice breaks a little bit over the words. “He actually said this to you?”
“I didn’t want to come here,” Isaac pouts. “I miss Erica. Derek says she won’t come back though. Boyd either. I want them. And Scott.”
“Yeah well, this isn’t my ideal situation either, kid,” Stiles says, reeling from the idea that Derek not only doesn’t hate him, but also said so out loud. “But Derek’s right. You can trust me.”
“Derek said you’re smart,” Isaac says, skeptically. “But he also said you smell better than Scott and that’s wrong, so he lies. Your dumb heart is being worse now,” he complains, and Stiles coughs guiltily. “It’s loud. Stop it.”
“Okay…” Stiles rubs his hand over his forehead, and his flushed face feels ridiculously hot under his fingers. “How many cookies is it going to take for you to never mention any part of this conversation to Derek, ever?”
Isaac considers the question very carefully. “Seventeen,” he says eventually, “and also cake.”
Stiles grins through his embarrassment and tosses him the half-full box of Thin Mints he’s been keeping in his drawer. “We should really become better friends once you’ve grown out of this, Lahey,” he says, watching fondly as Isaac stuffs three cookies into his mouth at once. “We’ve got very similar priorities.”