The Phelps Department Store owner Hiram Phelps has died, leaving half-ownership in the business to his nephew, singer Tommy Rogers. The other half is owned by Hiram's sister, Martha Phelps (Margaret Dumont), Tommy's aunt. Rogers has no interest in running a department store, so he plans to sell his interest and use the money to build a music conservatory. Store manager Grover (Douglas Dumbrille) wants to kill Rogers before he can sell his share, marry the wealthy Martha, then kill her to become sole owner of the Phelps Department Store. Martha is highly suspicious, worried about Tommy's safety lest anyone suspect her of foul play to take over the store. Against Grover's wishes she hires private detective Wolf J. Flywheel (Groucho) as a floorwalker and bodyguard. Between Tommy wooing his sweetheart Joan (Virginia Grey) and Flywheel romancing Miss Phelps, the brothers eventually expose and thwart the plot to kill Tommy.