In Hoboken, New Jersey, circus elephant trainer Bill Bogard is in love with gypsy violinist Princess Mitzie, but is unable to declare his love because he is poor and she is wealthy. Mitzie, attracted to Bill, is furious when she thinks he is snubbing her. When Bill learns that he has won the grand prize of the Grand National Steeplechase derby sweepstakes, held in Aintree, England, he turns flips and cartwheels and promises to give ten percent to his friend, Egbert Jackson, a black porter. Egbert, however, has placed Bill's ticket stub for safekeeping in the pouch of a boxing kangaroo. After the stub is retrieved, Bill kisses Mitzie, who slaps him and breaks a violin over his head. When he continues, she knocks him out. Frantic that she may have killed the man she loves, Mitzie kisses him, but she is then angered when he revives and she thinks he is fooling with her. However, he convinces her that he is sincere, and they plan a wedding ceremony to go with her farewell performance, as she and her band are returning to Hungary. Bill, however, does not show up for the wedding. The attending audience becomes angry, as does circus owner Charles O'Brien, who had secured a $50,000 bond from Mitzie's father in exchange for finding her a husband. While returning to Europe on the S.S. Austrilich , Mitzie becomes distraught. Unknown to Mitzie, Bill and Egbert have been kidnapped by hypnotist Professor Horace S. Limberly, who has the ability perform his powers on "chumps," and has brought the two onboard the ship to assist him in his act. Bill and Egbert come out of their trance while they are out at sea, and the shock of their location is minimized by the discovery that Mitzie and Egbert's girl friend Pearl, a black maid, are onboard. When Limberly learns that Bill has won $500,000, he hypnotizes him and Egbert again and robs Bill. After O'Brien gets them out of the trance, they learn that a suicide note has been left by Limberly saying that he will jump overboard. At the captain's table, when a Russian nobleman's beard catches fire, the captain spritzes him, causing his beard and wig to fall off to reveal that he is really Limberly. He threatens to blow up the ship and throws an object that the others think is a grenade. Egbert catches it and tosses it to the captain, and it gets lodged in a chandelier, then falls into Egbert's pants and out his leg before it is discovered to be an avocado. Egbert upsets Pearl, who throws a knife at him and hits him over the head with a bowling pin. He unwittingly hides in a box to be used in a lion act and finds Limberly already in the box. The box is rolled onto the stage, and after it falls apart during the act, the lion bites Egbert in the pants, while Limberly tries to pull the lion away by the tail. Limberly bites the lion's tail, and the lion knocks Egbert down and lies on him, whereupon Egbert bites the lion's tail and they wrestle. Meanwhile, Mitzie has caught Bill in a compromising position with a woman clad only in a slip. When he kisses Mitzie, she curses him in Hungarian and slaps him. After he kicks her, she threatens him with a knife, but when he only laughs at her, she begins to cry. Egbert suggests to Limberly that he hypnotize the lion, but the professor says that the lion does not look like a chump. He succeeds, though only momentarily, before the lion breaks the spell and chases them through the crowd, causing pandemonium. The passengers scramble for lifeboats, and Mitzie refuses Bill's pleas that she get into one. O'Brien and Limberly disguise themselves as women to escape in a lifeboat, but they are found out. Soon sanity is restored, as the professor ends up washing dishes on the ship, Pearl revives Egbert, who almost drowns in the ship's swimming pool, and the captain marries Mitzie and Bill.
