Neville St. Clair, a respectable businessman, has disappeared and his wife claims she saw him at the upper window of an opium den. Rushing upstairs to the room she found only a beggar who denied any knowledge of St. Clair - whose clothes are later found in the room, and his coat, laden with coins, in the River Thames outside the window. The beggar is arrested, but a few days later St. Clair's wife receives a letter from her husband. Holmes concludes, then proves, that the beggar is actually St. Clair in disguise; he confesse that he has been leading a double life as a beggar, making more money that way than in his nominal work.
