The Big Store (1941)

Private detectives Wolf J. Flywheel, Wacky and Ravelli (The Marx Brothers) are hired by the officious Martha Phelps (Margaret Dumont), co-owner of the Phelps Department Store. Her beloved nephew, Tommy (Tony Martin), has been assaulted, shortly after he announced plans to sell his share of the store. Unbeknownst to Martha, the culprit is her fiancé, sleazy store manager Mr. Grover (Douglas Dumbrille), who wants Tommy dead before the sale exposes his years of fraud and theft.