Joe Wilson was a poor, itinerant salesman with a pretty young wife in Philadelphia. Joseph Kent Gimball was a wealthy, socially prominent New Yorker with an elegant and aristocratic wife. These two very different men were actually the same man, a bigamist leading a bizarre double life. His deception was revealed to the world after he was murdered in his "halfway house," a riverfront shack outside Trenton, New Jersey, that he used as a hideout to switch identities. But who killed him? Ellery Queen, who is drawn into the case to help old friends, puts his finger on the central question: "Who was murdered -- Joe or Joseph?" Queen performs an extended feat of logical deduction from seemingly insignificant clues, such as a number of burnt matches, and finally develops a profile of the killer that can fit only one person in the case.