A younger, adopted sister for an accidental vampire? Their family was killed by a much older vampire while she was at a friend's. They thought he was the only survivor. There's vampire hunters sniffing around, and she's desperate not to lose him, too. They were always a little co-dependent, so it seems natural that she'd offer herself to keep him from prowling. Except that it spirals rapidly out of control for her, and she's left wondering if this is what he wanted all along.