After being marked by The Hollow's dark magic, both Klaus and Marcel experience the symptoms of a malevolent haunting, forcing the two adversaries on a violent collision course. Meanwhile, Hayley and Elijah head out to speak with Mary after Hayley uncovers a mysterious link between the dark magic and her former wolf pack. Finally, as an exhausted Freya risks her own life to cure Klaus' infection, a guilt-ridden Keelin must decide whether to honor her hypocratic oath and help Freya – or flee the Mikaelson's forever.