Derek is being pressured by his family to pick a mate, and somehow stumbles into a choice that they didn't expect and aren't sure they approve of....

Derek thinks that the mating rituals are overly romanticized bullshit, but claiming a mate and defending them from challengers is something werewolves do, and his pack can't afford to appear weak after the fire. Especially not when Deucalion and his friends are in town for the rituals. Enter Stiles Stilinski, who offers to let Derek claim him so he won't be overrun at the ceremonies. Nothing goes as expected.

“Well,” Stiles says, “if they’re going to hunt werewolves, I’m going to hunt them.” It’s a ridiculous statement from a ten-year-old, but he’s obviously one hundred percent sincere. For the first time since the fire, Peter feels life stir inside him, feels purpose. It’s kismet, clearly. He’ll never meet the child he would have had with Olivia. Instead he’s met this boy, this brilliant, determined, cynical child with a world of potential. Peter kneels down in front of him so they’re at eye level. “How do you feel about doing that together?”

To keep the peace between the Shadowhunters and the Downworlders, a treaty designates an intermarriage between the two groups every seven years. Alec isn't exactly happy to be chosen, but then he finds out that his intended is nothing like what anyone expected.