One of Sir Henry Merrivale's best works. The mystery of the “closed room”, elevated to the absolute and honed to brilliance. G.M. appears as the lawyer for Jimmy Answell, who is accused of murdering his fiancee's father. He was found in a closed room, alone with a dead man, his fingerprints were on the murder weapon, the story he told looks like utter nonsense. And only Sir Henry knows for sure that the defendant is innocent, knows how the murder was committed, and who committed it. The question is whether he will be able to convince the judge and jury of the correctness of his version during the trial.