Dr. Watson returns to the Baker Street flat in a state of great agitation. He tells Sherlock Holmes that, earlier in the evening, he had attended a dying man in his final moments, only to see the same man in the street soon afterward, and be punched in the eye by him. Holmes is intrigued, and goes with Watson to check the dead man's lodgings and to view his corpse in the morgue. The detective learns that the man had been a watchman at an art museum, and that he had a previous conviction for counterfeiting. The next evening, when Watson returns to Baker Street convinced that he has seen the same dead man once again, Holmes puts the clues together and goes to warn Inspector Lestrade about an impending crime at the museum.