Dead by Saturday — S. Fowler Wright

Basil stumbles across a briefcase full of money on a London street. He changes his name and tries to stay one step ahead of the real owners of the cash--a group of American gangsters. But Inspector Cleveland of Scotland Yard knows that he has a major problem on his hands, and needs to find the hapless man before the crooks do. Can Basil remain free--or will he become Dead by Saturday?