“Thin Lizzie” gives viewers a Supernatural Monster of the Week episode with an unexpected twist, reminding us that “The Darkness is coming for us all.” It might even be standing in the bushes spying on you. With his fascination for serial killers, Sam (Jared Padalecki) can’t resist investigating a couple axed to death while staying at the Lizzie Borden Bed & Breakfast Museum. Dean (Jensen Ackles), on the other hand, isn’t thrilled to stay in a flowery room that smells like lavender toilet water. It turns out that Sam isn’t the only one with a “freaky fetish” for Lizzie Borden, because Amara also can’t resist visiting the home of this famous axe murderer. Who knew Sam and Amara had so much in common.