Four stowaways, Groucho, Harpo, Chico and Zeppo, are discovered aboard a luxury liner and are chased for the entire voyage by Captain Corcoran and his crew. At various times during the chase, Harpo becomes part of a Punch and Judy show, and Chico and Harpo impersonate the barber. Groucho hides in a closet in gangster Alky Briggs's stateroom, and when Groucho emerges from the closet, he finds Lucille, Briggs's wife, alone and flirts with her. Briggs suddenly comes in, and after Zeppo also bursts into the room, Briggs hires Groucho and Zeppo as his bodyguards. Meanwhile, Chico and Harpo wander into rival gangleader Joe Helton's room to play a game of chess and become his bodyguards. Briggs enters Helton's stateroom and announces his takeover of Helton's territory, but Helton orders him out, with the help of Chico and Harpo. Groucho later hires himself out to Helton as his personal bodyguard in an attempt to baffle logic. When the ocean liner docks, the stowaways try to impersonate singer Maurice Chevalier, whose passport Zeppo stole, but are unsuccessful. When a man faints, the stowaways hide in his stretcher and are carried off the ship. Later, Mary Helton is kidnapped at her coming-out party by Briggs's men and is held in the barn. Because Briggs has told Groucho of his plan, Groucho and the boys warn Helton and then go to the barn. A fight ensues, during which Zeppo rescues Mary and later knocks Briggs out just as Helton arrives.