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...