Wealthy Madame Rosepettle (Rosalind Russell) and 25-year-old Jonathan (Robert Morse) arrive at the Port Royal Hotel on a tiny Caribbean island with the man of the family in tow, literally; he's been dead for many years and his stuffed corpse travels with them in a coffin. Madame is the kind of woman who keeps piranhas and Venus Flytrap plants as pets, and controls her son's life down to deciding what meal he'll have for breakfast, lunch, and dinner (a hamburger and a maraschino cherry). Jonathan is kept indoors at all times and isn't allowed to mix with the outside world, though the hotel "babysitter," Rosalie (Barbara Harris), slips in through the window and flirts with the easily rattled young man. Madame is being courted by drunken millionaire Commodore Roseabove (Hugh Griffith), and while she welcomes his advances, her attention is diverted by trying to make sure that her son stays "pure." Rosalie isn't one to be put off by the meddling matriarch, so she doubles her efforts to get at Jonathan, who wants Rosalie too but might be pushed over the edge by the attention.