Characters dressed in the garb of 17th century plague doctors roaming alleyways haunted by Jack the Ripper… A plague victim vanishing off a stretcher under the noses of witnesses a few feet away… The corpse of the same victim reappearing under the nose of a police officer half a mile away. How are such things possible in the London of 1938? Are the events connected to a conversation overheard between a celebrated writer of mystery plays and his principal actor, where each accepts a challenge to commit a murder and pin it on the other? And what is the connection to a replica of Maelzel’s chess-playing robot? The famous criminologist Dr. Alan Twist and Inspector Archibald Hurst of Scotland Yard face one of the most diabolically clever criminals in their long collaboration.