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.

Ellery Queen, who is drawn into the investigation to help old friends, is able to look beyond the strange nature of the victim to seek hard facts.

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.

This period in the Ellery Queen canon signals a change in the type of story told, moving away from the intricate puzzle mystery format which had been a hallmark of the nine previous novels, each with a nationality in their title and a "Challenge to the Reader" immediately before the solution was revealed.

"Halfway House" is the last novel wherein Queen issues his "Challenge," and it is the first without a "nationality title," although it is remarked in the foreword that the story could have been called The Swedish Match Mystery.