Hugo Z. Hackenbush (Groucho Marx) is a veterinarian who is hired as chief of staff for the Standish Sanitarium, owned by Judy Standish (Maureen O'Sullivan), at the insistence of her most important patient, the wealthy Mrs. Emily Upjohn (Margaret Dumont), who insists on being treated only by Dr. Hackenbush. The Sanitarium has fallen on hard times, and banker J.D. Morgan (Douglas Dumbrille) is attempting to gain control of the sanitarium in order to convert the building into a casino. Judy hopes that Mrs. Upjohn will make a large donation and prevent that from happening.