The discovery of a corpse turns a cross-country train journey into a closed-circle hunt for a killer. The magnificent Transcontinental Express, showcasing the cutting edge of mid-1930s luxury train travel, is making its first trip from New York to San Francisco. For its record-breaking maiden voyage - coast to coast in three days with no passenger stops - the express carries only invited guests, among them renowned businessmen, physicians, psychologists, and even a high-ranking member of the NYPD. Among refined staterooms, an elegant dining car, and a “recreation room” for bridge, ping-pong, and dancing, the vehicle’s most lauded feature is the swimming pool car - which is precisely where the waterlogged corpse of a prominent banker is discovered just one day into the journey. Uncertain of the cause of death and fearing negative publicity, the conductor drives on for the West Coast, charging a select group of passengers, including the sharp-witted Dr. Pons, with the task of uncovering what has occurred - even as every new piece of evidence seems to suggest more perplexing possibilities.