The Disappearance Of Mr Davenheim

The impeccable Belgian detective is eager to solve the case of a mysterious disappearance of a city banker. He lays a bet with Inspector Japp that he can get to the root of the matter without even leaving his apartment. Japp hops onto this easy money deal. Will Poirot find success in figuring out what happened to the banker who went out to post some letters and never returned?