Kate receives a letter from a Mr. Donald Dobble requesting a reservation for two rooms for him and a friend. Mr. Dobble's friend, David Benton, arrives and acts as though Dobble were with him. But Kate sees no one but Mr. Benton. Mr. Benton seems crazy as he sees and talks to an invisible man. Kate believes that Mr. Benton is probably overworked. When no one else seems concerned that they haven't seen Dobble, Kate starts to feel that she is the one going crazy. Kate continually tries to sneak a peak at or speak directly to Mr. Dobble to no avail. The girls start to worry about Kate, especially when they see her talking to no one. Kate asks Benton and Dobble to leave and to not worry about paying their bill. A Mr. Robinson comes by looking for Benton. It seems Benton defrauds hotels into getting free room and board with his invisible man scheme.