Accident-prone busboy Myron Mertz (Jerry Lewis) and his suave nightclub-crooner pal, Larry Todd (Dean Martin), get caught up in both a gangland slaying and a mystery involving the comely Mary Carroll (Lizabeth Scott). She has just inherited an island castle off the coast of Cuba that her lawyer, Cortega (George Dolenz), insists is overrun with ghosts and zombies. Attempting to save Mary from a mysterious stranger who wants her dead, Myron and Larry sail with her to Cuba.