As a train speeds through the Arizona night, a man posing as a physician holds up the baggage-car crew and escapes with a $500,000 payroll. The fake doctor, Paul Bruckner, leaves the train with his "patient" and the "patient's wife", who is really Bruckner's wife Linda. The insurance company puts its best investigator, Charlie Norman, on the case to work with the railroad's investigator, Joe Armstrong. The men are friends and Joe is upset that Charlie and his wife, Ruth, will have to postpone their Mexico vacation. Charlie's concern goes beyond the spoiled vacation as he was the brains behind the holdup, who had fallen in love with Linda several months earlier while investigating a claim Bruckner had filed against his insurance company. At first, Joe is unable to find anything out about the flawlessly timetable planning for the robbery other than what Charlie wants him to find out.