Chan and son Lee find two murderers trying to get away with money from counterfeit bonds.
Charlie Chan (Warner Oland) arrives on a plane, gives money to a beggar, and calls dancer Nardi (Dorothy Appleby). A note thrown in his taxi warns him to leave France. Chan tells Victor (Thomas Beck) he wants to go to the Lamartine Bank. Chan meets Yvette Lamartine (Mary Brian) and Max Corday (Eric Rhodes), who sketches him. They go to see Nardi dance, and he sees the same beggar. Nardi nods to Chan and dances. The beggar throws a knife at her. As she dies, she tells Chan to look in her apartment. There he finds a note that Albert Dufresne (John Miljan) lost money gambling. A man on the roof drops a block near Chan. In his room Chan finds his son Lee (Keye Luke). Chan is investigating bond fraud for a London bank.
At the Lamartine Bank Yvette asks her father for 1,000 francs. Albert will return her love letters if she comes to his apartment; she angrily walks out. The beggar complains loudly and is identified as crippled war veteran Marcel Xavier. Chan says, "Kindness in heart better than gold in bank." Lee follows Albert. Yvette has her fiancé Victor take her home, because she is sleepy; but she goes out in a taxi. Albert is packing; he gets a call and says he has 2,000,000 francs in his box at the bank. Lee sees Yvette go in. As Albert is handing her the letters, a man sneaks in and shoots him. Yvette picks up the gun and is arrested. Lee sees the beggar come out and follows his taxi.
The police inspector tells Chan that Nardi was seeing rich men. Yvette refuses to say why she was there. Chan finds a broken seal. Max Corday arrives drunk to see Albert. Yvette gives her letters to Chan. Bank employee Henri Latouche (Murray Kinnell) arrives. Chan shows the police that someone entered from the balcony. Lee tells his father he followed the beggar and saw him transfer to Corday's car. Chan and his son catch Corday running away and tie him up. At the bank Chan gets Xavier's address. Victor takes him there. Lee hears a phone call of a man saying he will meet Corday at Xavier's. Chan and Victor go down the stairs at Xavier's into the sewers, where they find counterfeit bonds and a printing machine. Xavier comes in and shoots at the flashlight that Chan taped to a broom. Victor makes him drop his gun. The police arrive, and Chan reveals that Xavier is Latouche and also Corday at times. He asks the police to release Yvette.
Chan gets help from his obedient son for the first time. His thorough detective work outsmarts the criminals and the police as usual.