In Monte Carlo, Paul Gaillard, an impoverished Russian exiled aristocrat, has a fabulous run of luck at the baccarat table. His winnings, ten million francs, are so vast he needs a suitcase (which he brought with him) to carry away the banknotes. The management desperately tries to entice him to stay, strewing various signs of good luck—four-leaf clovers, a horseshoe, even a hunchback—in his path, to no avail. Even worse from their viewpoint, Paul is quoted in the newspapers advising people to stay away from Monte Carlo.
On the train, Ivan accompanies him, and in Paris at the Cafe Russe, he shares the money with the staff who had scrimped and saved for ten years to build up their initial stake.
The next day, Paul and his servant take the train to Interlaken, Switzerland. By chance, Helen Berkeley is mistakenly placed in Paul's compartment. He takes the opportunity to try to charm her, but she rebuffs him. He is delighted, however, to learn that the man with her is her brother, Bertrand Berkeley. Paul pursues her with great persistence, and it finally pays off. They spend time together.
Then Helen confides that she is unhappy because she is going to marry a 63-year-old for money, not for herself, but for her brother, who needs 5 million francs. Paul offers her nearly 4 million, his share of the winnings. She does not accept, but asks him to spend a week with her in Monte Carlo. He agrees. It turns out she is a back street music hall performer who was hired to lure him back, but she cannot go through with it, having fallen in love with him. Too ashamed to face Paul again, she secretly departs for Paris. When he discovers she has vanished, he makes a bargain with her brother: he will get the money Bertrand supposedly needs desperately in return for his sister's location. Bertrand lies and tells him that she went to Monte Carlo. Helen runs into Bertrand at the train station and learns what he has done. She rushes to Monte Carlo.
Paul returns to the baccarat table. When Helen enters the club to try to stop him, she is intercepted by the management and kept a virtual prisoner. Paul loses nearly all his money, but then his luck changes and he goes on another winning streak and he is on the verge of breaking the bank again. However, he loses everything on the last bet. When Paul leaves, he sees Helen and Bertrand emerge from the manager's office; he congratulates them. He returns to work driving a taxi.
By chance, he takes a fare to a nightclub where Helen is performing. He dons his black tie and tails and goes inside. He dances one dance with Helen and pretends to still be fairly well off, before driving away. Helen chases after him in another taxi, finally catching up with him at the Cafe Russe. When she discovers he is the driver, not a passenger, she is ecstatic. Now that he is poor, she can tell him that she loves him. They embrace. Then he takes her inside the closed Cafe Russe, where the staff, Russian nobility like him, are privately celebrating the late Czar Nicholas II's birthday in a grand manner.
