Inspector Maigret receives a call from his wife to say he has a visitor at their apartment. 

But when he gets home, the young man has already gone, along with Maigret's prized Smith and Wesson .45. The trail to find the culprit - and the woman who may become his victim - takes Maigret across Paris and all the way to the Savoy Hotel in London.

But getting to the truth may be even more complicated than he had first imagined.