Elle used to love her boyfriend. Their relationship used to be so good. But not now, not anymore. Now their relationship has become so stale, so boring.
Not that that was a good reason to cheat - there was never a good reason to cheat. And Elle didn't mean to sleep with that guy from the club; it just sort-of happened.
Now Elle has caught something. Now she's infected. Now her sexual desires are uncontrollable. And this infection - whatever it is that has found a home between her legs - has a taste for human flesh.
