 Just minutes before his business rival Gerald Lowen arrives to meet with him, banker Matthew Davenheim tells his wife he is going to post a letter, steps out of his home into the fog, and disappears. When his wife discovers a few days later that the safe in which her missing husband stored a variety of precious jewels he gave her as gifts has been broken in to, the jewels stolen, Poirot suspects that Mr. Davenheim s disappearance may not be the real mystery, but perhaps the mystery lies in the missing jewels. With Captain Hastings as his eyes and ears on the scene, Poirot accepts a bet from Inspctor Japp that Poirot cannot solve the mystery without leaving his London flat. Of course, Poirot solves both mysteries...but how?