Fever/delirium ought to work for any fandom with secrets, right? I don't know which characters on Travelers you like, but you could apply this to almost any of them. MacLaren and his wife, maybe?

Blackmail...I kind of want to see someone blackmail one of the vampires on BHUS. Someone who knew enough to take precautions, maybe. Unless they didn't know what they were really dealing with? Though in that case, they might not live long.