Inspector Gadget attends a cruise in order to safeguard the passengers' expensive jewelry. Despite the efforts of a MAD milkman and his exploding milk bottle, a bothersome seagull who seems to have taken a liking to the police inspector, and two MAD agents who won't let anyone on the ship without an invitation, Gadget manages to get aboard. Little does he know that Dr. Claw is also on board and he's replaced the entire crew with his own men. Penny does some investigating of her own below deck, but is soon captured. Upstairs at a cocktail party, Gadget suspiciously eyes various guests until the lights suddenly go out. Panic breaks out when guests' jewelry is plucked from them in the dark. While Gadget continues interrogating passengers, Claw gets ready to get rid of the kidnapped crew. Hoping to force some sort of showdown, Brain guides Gadget downstairs into a rat's nest of MAD agents, who presumably overpower him. He's soon strung up on the cable of a crane, and is mercilessly and repeatedly dunked in the ocean by Dr. Claw, toying with him like a cat plays with a mouse. The police (and the Coast Guard) arrive just in time to capture the MAD agents, save Gadget and the crew, and prevent the jewels from disappearing. Claw, however, manages to make a last-minute escape.