The Mark of the Beast — Kim Antieau

On his way to M. Garnier's chateau, Jean-Jacques Rieux gets lost in the forest and is rescued by a mysterious woman who turns out to be Garnier's much younger wife, Marie. Garnier claims she has the mark of the beast on her because her parents were killed by werewolves. As Rieux observes Garnier's cruel treatment of his wife, he begins to wonder which one of them is the beast. (short story)