While on his yacht in the South of France, Tony Newlander, a very wealthy man, realizes that he has no friends and that he is surrounded by people who are only interested in his fortune. Tony dives into the Mediterranean to save a drowning man, and after the rescue, learns that the poverty-stricken man, named Louie, attempted suicide. Louie takes Tony to his shack by the shore, where Tony reveals his identity and remarks that he would give at least a million francs if he could find just one person who was kind without expecting to get paid for it. The next morning, Louie awakens to discover that Tony has switched clothes and gone, leaving Louie a wad of bills. In town, a reporter hears Louie's story and brings him to his editor, who prints the story that a millionaire, disguised as a tramp, will give a million francs for a kind deed. Tony, meanwhile, wanders through town, and after he tries to help an American circus girl named Jean catch her runaway chimpanzee named Darwin, Tony is arrested on suspicion of setting off a fire alarm, which Darwin actually pulled. As the judge is about to pass sentence, he reads about the millionaire tramp in the newspaper and, believing Tony to be the millionaire, gives him his liberty and a calling card. That day, Tony, in puzzlement, witnesses citizens bestow a number of acts of kindness on various tramps before he sees Louie's picture in the newspaper and learns of the story. Meanwhile, when Tony's supposed suicide is discovered on the yacht, Corcoran, a former associate, destroys the ship's radio so that the news cannot be relayed and thus cause a drop in Newlander securities before he can sell them. At the circus, owner Anatole Primerose lets all the tramps in for free, and Tony brings Jean flowers. She gets him a job as nightwatchman, to the dismay of Primerose's son Max, who is in love with her. The Riviera soon becomes a vagrant paradise as tramps arrive by the trainload to take advantage of the kindness alloted them by citizens who hope to get the promised million francs. When the city is overrun, and the citizens demand that the editor produce the millionaire, the editor fires the reporter. To regain his job, the reporter then charges that Louie probably murdered the millionaire. After threatening to turn Louie over to the police, the editor gives him a chance to identify the millionaire among the tramps whom the prefect of police has ordered to be rounded up. When Tony is about to be arrested, Jean convinces the gendarme that he is an employee. Jean tells Tony that she hopes to leave the circus someday and settle down in a house for the sake of her Uncle Victor, a circus clown who has taken care of her since her parents died. Tony admits that he is now getting a kick out of life because of Jean. Their subsequent embrace and kiss is heard by Max, who threatens to have Jean fired. To save her job, she tells Max that Tony is the millionaire of the story and that she is only playing up to him and plans to give Max half of the million francs. Tony overhears their conversation and leaves, now cynical about everyone. When he tries to have ten thousand francs wired to him and identifies himself to the telegraph clerk as the millionaire, the clerk calls the police, but just then Louie, fearing the editor, pronounces that a tramp in the police lineup named Kopelpeck is the millionaire. The clerk, told this news, calls Tony a fraud. Taken to the imperial suite at the town's hotel, Kopelpeck attempts with Louie to steal as much silverware as he can, but when some items fall from their clothes as they run out, the fraud is exposed. Meanwhile, Tony has been arrested for claiming to be the millionaire, and Victor overhears the judge sentence him. He tells Jean that Tony has gone crazy and thinks that he is the millionaire. Greatly concerned, Jean and Victor rush to the judge with bail money that she finagled from Max. At the court, Jean explains to Tony why she "lied" to Max, but when the captain of Tony's yacht arrives and identifies him, Jean is cold to him, thinking that he was laughing at her all the time. After an angry mob of citizens complain about all the money they have spent entertaining tramps, Tony agrees to divide the million francs between the poor and the city, if Jean will marry him. She refuses, saying that she was in love with a poor tramp who needed her, but when Tony convinces her that he still needs her, she agrees. At the wedding, guests scratch as fleas from an invited tramp circulate among them.
