During World War II, just after King Hubertus II of the Balkan country of Barovia, announces that Barovia will hold its first democratic election, he is shot by a member of the Mordia, a secret society that is planning a coup d'état . As the king, who is last of the Banocheks, lies dying, he tells general Katrina Grimovitch that while visiting America in 1915 he married and had a son who is now living in New York under the name Michael Valentine. Grimovitch, Minister of War Grubitch, Finance Minister Zavitch and Premier Krivoc secretly fly to New York to bring Michael back to Barovia to assume the throne before the Mordia takes over the country. Michael, a radio announcer whose sponsor is Sparko Dog Food, is about to be married the next day to Hazel O'Brien, whose male relatives are all policemen. Grimovitch, Grubitch, Zavitch and Krivoc kidnap Michael and attempt to take off in a plane, but are grounded when one of the Mordia shoots at them. The general hides Michael at the Park Villa Hotel under constant guard. The next morning, Hazel and her hot-tempered brother Victor await Michael to begin the wedding, which has been staged as a publicity stunt for Sparko Dog Food. At the hotel, Grubitch is slain with a knife meant for Michael, who is chased by two members of the Mordia and escapes into the hands of two policemen who have been ordered by Victor to arrest him. At the police station, Michael explains his predicament to Hazel and Victor and to prove his story, takes them to the hotel to find Grubitch's body, but it has been hidden. Victor, believing Michael made up the story of the Barovians to get out of marrying Hazel, leaves with her in a huff, while the general locks Michael in the maid's linen closet to protect him. Michael escapes to his apartment, where Grimovitch is waiting for him. They sleep, separately, and in the morning, Hazel and Victor visit and, finding Grimovitch in a nightshirt, assume the worst and walk out. In grief over Hazel, Michael shows Grimovitch how Hazel used to kiss him, and decides that he likes kissing Grimovitch even better. While fleeing the Mordia, Grimovitch and Michael end up in a department store, where Michael is picked up and taken to the Barovian consulate, the Mordia's secret headquarters. Both Krivoc and Consul Paul Stertorius are double agents. While the Mordia, hooded, draw straws to see who will execute Michael, he enters through a heating duct and dons a hood, then picks the longest straw. He fakes the execution, and while they chase him, crawls through a duct and emerges in the consul's office, where he helps Grimovitch hold up Stertorius. Meanwhile, Victor and his policeman friends have discovered Grubitch's body at the hotel and arrive at the consulate in time to round up the Mordia. Grimovitch and Michael then board a plane and are joined by Krivoc, who exposes himself as the last of the Mordia. Michael foils Krivoc with a trick cigar that explodes. The pilot then receives a call from Zavitch, who tells them that Michael is not the king's son. The Mordia have siphoned the fuel tank, and as they return to LaGuardia, the plane plummets toward the ocean, prompting Grimovitch to confess her love to Michael. The pilot switches to a reserve tank, and Grimovitch and Michael kiss.
