Someone knocked out a man and left him for dead during a fishing trip in Portugal. That someone is either his fetching wife, or two business partners, all sporting guilty faces after his unexpected return. Two more murders and a frame-up befall the quartet before an inspector closes the case.

A gang of four would-be robbers plans to steal a fortune in currency hidden aboard the "Flying Scotsman" in a railroad stateroom by cutting through the wall of the adjacent stateroom, but find themselves up against numerous unexpected drawbacks, including interference by their fellow passengers.