Based on

Movies like Seven Sinners (1936)

Ed Harwood, a wisecracking private investigator from New York, discovers a crime at a hotel in Nice during a carnival. The unraveling of the mystery which lies behind will lead him and Caryl Fenton, a female insurance agent, who will become his companion, first to Paris, then to London, later through the English countryside and finally to Southampton, in search of a criminal train wrecker.