Michel René Lefèvre Bouflette, a debt-ridden artist, is interrupted repeatedly while courting Vanda Vanda Gréville, the woman he paints. His day is disrupted by his roommate, Prosper Jean-Louis Allibert; by his neighbor and fiancée, Béatrice Annabella; and by a chorus of creditors. As Michel tries to manage this chaotic day, Prosper discovers that Michel has just won a lottery worth a million Dutch florins—a fortune that could change everything.
The ticket is in the pocket of a jacket Michel gave Béatrice to mend, but she has lent the jacket to a charming criminal to help him elude the police. Beatrice gradually remembers the criminal’s name: Grandpa Tulip. With this clue, Prosper convinces Michel to agree to split the prize money if he recovers the ticket, and he begins a determined search. When Beatrice recalls Grandpa Tulip’s address, Michel sets out as well.
At the junk shop Grandpa Tulip runs as a front for his crime, Michel discovers that an Italian operatic tenor, Ambrosio Sopranelli Constantin Siroesco, had already come by and bought the jacket to use as part of a costume. One of Tulip’s associates stole a pocket watch from the singer, and he shows it to Michel, hoping the name inside might be there. While Michel inspects the watch, the police raid the shop and Grandpa Tulip and his men slip away, leaving Michel to be arrested.
The police think Michel is Grandpa Tulip, so they summon Prosper to identify him. While Michel is waiting, the tenor arrives to report the theft of his pocket watch, and Michel learns that the man’s name is Ambrosio Sopranelli and that he is singing at a local theater, but will soon travel to America. Michel relays this information to Prosper when he arrives, but Prosper acts as though he does not know Michel so that Michel will stay imprisoned and Prosper can be the one who recovers the ticket. Eventually, Michel’s creditors arrive to identify him, and he heads to the opera house.
Disregarding his guilt, Prosper visits Vanda and seduces her with tales of his imminent fortune. He tries and fails to get the ticket from Sopranelli’s dressing room, and so does Vanda. Michel asks Béatrice, who is one of the dancers during the performance that evening, to try to get the ticket, but Sopranelli is called to the stage before she can. During Sopranelli’s first musical number, Michel and Béatrice reconcile.
Grandpa Tulip and his men go to the opera house to find out why Michel was so desperate to regain the threadbare jacket. Beatrice sees him backstage, however, and, to repay her for helping him earlier, he promises to make sure the jacket is returned to her. Meanwhile, Michel and Prosper end up on stage in pursuit of the ticket. When the curtain comes down, they grab the jacket and find themselves pursued by both stage managers and Tulip’s men. The jacket gets passed around like a football, is accidentally thrown out a window, and lands on top of a passing car.
After the performance, Michel and Beatrice head home in the taxi Michel has been riding in all day while ignoring the driver’s demands for payment. Michel discovers this is the car on which the jacket landed and has the driver stop, but, before he can remove the ticket from the pocket, some of Grandpa Tulip’s men pull up and seize the jacket.
Dejected, Michel and Beatrice discover his creditors are throwing a lavish party in his apartment, to be paid for out of the lottery winnings. As Michel is about to give everyone the bad news, Grandpa Tulip enters with the jacket. Michel cannot find the ticket inside, but, when it becomes clear to Grandpa Tulip that it is what Beatrice really wanted him to return, he hands the ticket over, having removed it from the jacket before coming over.
