The story takes place in the early 18th century. The two main characters are faculty members at King's College, Cambridge who dabble in the occult and believe themselves to be magicians. One night, they go to the grave of a recently deceased woman who was reputed to be a witch in order to obtain materials to use in their spells. They take precautions to protect themselves against any demons that might be in the locality. They find, however, that those precautions are ineffective.