Private eye Edward Mercer (Richard Todd) travels to Venice to locate a man due a reward for his aid in the war. Shortly after arriving, he becomes the prime suspect in the murder of his local contact. In his quest to clear his name, Mercer uncovers a conspiracy. Even the local magistrate (George Coulouris) seems to be working against him, and Mercer begins to suspect the man he came to find is behind it all.
