Oliver "Puddin' Head" Johnson (Lou Costello) and Rocky Stonebridge (Bud Abbott) are on their way to Death's Head Tavern, where they work. They encounter Lady Jane (Fran Warren), who asks them to bring a love note to the tavern singer, Bruce Martingale (Bill Shirley).
At the tavern, the notorious Captain Kidd (Charles Laughton) is dining with Captain Bonney (Hillary Brooke), a female pirate. She accuses Kidd of raiding ships in her territory and is asking for restitution. Kidd informs Bonney that he has hidden the amassed treasure on Skull Island, and that only he has the map to its exact location. He agrees to take her, with her ship in tow, to the island so that she can receive her share. During the discussion, Oliver happens to be waiting on them, and inadvertently switches the map for the love note that he was carrying. Rocky discovers the mistake and goes to Captain Kidd, demanding a share of the treasure and a place on the voyage in exchange for the map. Kidd ostensibly agrees, but intends to kill Oliver and Rocky once he gets the map.
The voyage begins (with the addition of Bruce, who has been shanghaied), and Kidd unsuccessfully attempts to regain the map throughout the entire voyage. (Meanwhile, Bonney mistakenly believes that Oliver wrote the love note and has now fallen for him—further complicating the whole situation). During the voyage, Kidd raids another ship, which happens to have Lady Jane on board, and she is kidnapped.
The two ships finally arrive at Skull Island; Oliver and Rocky begin to dig up the treasure, when Kidd arrogantly declares his plans to dispose of them along with Captain Bonney. They alert Bonney to Kidd's true intentions, and her crew attacks. The treasure is recovered, and Bonney's crew wins the fight, with Kidd becoming her prisoner.(synopsis from Wikipedia)