The narrative unfolds through the perspective of a narrator dining with a detective, Thorndyke, at a restaurant. Their evening is interrupted by the presence of an eccentric man, who later becomes a focal point of intrigue. The story shifts to a case involving a gang of jewel thieves, particularly focusing on a man named Shemmonds, who is suspected of being involved in a series of burglaries. The police, led by Superintendent Miller, are on the trail of this gang, which has been remarkably elusive, with stolen items disappearing without a trace. Miller reveals that one of the gang members, Shemmonds, was last seen with an elderly man named Luttrell, a dealer in antiques and jewels who possesses a strong-room secured by a complex puzzle lock. The police suspect that Luttrell may have been murdered by Shemmonds, who could be lying low with the stolen goods. The narrative builds tension as the police attempt to locate both men, leading to a series of events that culminate in a visit to Luttrell's premises. Upon inspection, Thorndyke discovers that the strong-room door is not locked as they initially believed. When they open it, they find the bodies of both Luttrell and Shemmonds, revealing a violent confrontation. The circumstances of their deaths raise questions about how Shemmonds ended up dead inside the strong-room, especially since he had the opportunity to escape. Thorndyke deduces that the puzzle lock's mechanism is more complex than it appears. He realizes that the lock's combination is encoded in a Latin inscription found on Luttrell's seal, which he cleverly deciphers as a Roman numeral. This revelation not only explains the lock's operation but also ties Luttrell to the criminal activities of the gang. The story concludes with the police using the information gleaned from Luttrell's journal to apprehend the remaining members of the gang, effectively bringing the case to a resolution. The intricate plot weaves together themes of deception, intelligence, and the consequences of greed, showcasing the detective's analytical prowess in solving a seemingly insurmountable mystery.
By R. Austin Freeman · First published 1910 · Genre: Mystery, Detective Fiction, Crime