The story's main character is a British historian named Anderson who travels to the town of Viborg in Denmark to do some research. During the course of his research, Anderson discovers that, in the early 16th century, Viborg was home to a man accused of witchcraft whose name was Nicolas Francken. Anderson stays in room 12 at the Golden Lion hotel. The Golden Lion is one of the oldest buildings in Viborg because it was one of the few structures to survive a devastating fire in 1726. A blackboard in the hotel lists all the rooms and the names of their occupants. Anderson sees that there is no room 13 listed on the blackboard. He does, however, see a door with the number 13 on it next to his own room. Anderson later realizes that room number 13 only appears at night and vanishes in the daytim