Dr. John Watson treats a patient who has lost a thumb. The patient says that the loss of his thumb was not an accident but the result of an attack. However, he fears that the story behind the loss of his digit is so strange that the police will not believe it.
A London lady comes to Holmes in curiosity about her newest lodger. After first renting the room, arranging for meals and newspaper to be left at the door, and paying a very high fee, he disappears completely. Or, is it someone else now inside the room?