The time is the 1890s, and Captain Sam (Henry Travers), owner of the showboat River Queen, is travelling from port to port along the Mississippi River, bringing his entertainment to each town. During one stop, in the river town of Ironville, he meets up with three individuals, Crawford (Alan Curtis), Bonita (Rita Johnson), and Bailey (Joe Sawyer), who are hiding from the local sheriff. Against the advice of his daughter Caroline (Lois Collier), his lead actor Dexter Broadhurst (Bud Abbott), and his chief roustabout Sebastian Dinwiddle (Lou Costello), the Captain joins them for a card game at a local gambling house.