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The author himself included this story in his list of 12 favourite Sherlock Holmes stories.

The story takes place a few years after Holmes' Last Case, where the protagonist allegedly dies during a fight with the head of the London underworld, Professor Moriarty, near Reichenbach Falls.

Thanks to his close friendship with Holmes for many years, Watson became interested in all kinds of criminal cases. The case of the tragic death of Ronald Adair particularly excited Watson. Ronald Adair belonged to the cream of society and had considerable wealth. He loved to play card games. One evening after a game, Ronald returned home to his room and locked the door from the inside. From that moment on, not a single sound came from Ronald's room. When the door was broken down, Ronald Ader was found dead. Later it was established that he had been killed by a revolver bullet, which seems impossible, because no one had entered the locked room. Holmes suddenly appears to help solve the mystery.