Something was wrong with him. Something other than dealing with possession and crushing guilt about the deaths he caused, worrying about his friends and father, worrying about supernatural threats.

Derek sighed again, "There's something Stiles needs to understand" he said "It's a known fact that Werewolves are very possessive. That's why Lydia and Allison haven't been targeted because they smell like their mates – like pack" Stiles' eyebrows furrowed "Why don't I smell like pack" he was clearly offended. "It's quite hard to smell like pack when you're not a wolf or sleeping

It was a business deal of sorts. One that came to fruition because Stiles was such a freakin awesome best friend and because Derek... well, Derek needed to mate.