In 1935, French diplomat David Talbot's happiness over his recent marriage to the beautiful Lucienne and his impending appointment as ambassador to Brazil, is dampened when he receives a strange, unsigned letter. Addressed to "Jean," the letter asks for one million francs to satisfy an old debt. David later leaves a package at the suggested drop-off point, but when the man who sent the letter, Carlos Le Duc, retrieves it, he is immediately arrested. At his trial for extortion, Le Duc testifies that the letter was merely an honest request for repayment and claims that he knew David from 1919 to 1922, when David was known as Jean Pelletier, a notorious criminal. The case becomes a news sensation, and the next day it is revealed by David's friend, Dr. Andre Tessier, that David had been in a train wreck in 1922 and suffers from amnesia. Tessier's theory of amnesia is challenged by Dr. Alex Dubroc, then a mystery witness, singer Michele Allaine, corroborates Le Duc's story and identifies David as Pelletier. Just then, wine salesman Henri Sarrou presents himself to the court and says that he knew Pelletier, who died years before. Some time after De Luc's conviction, Sarrou comes to see David and demands one million francs. Sarrou says that he and Pelletier had been cohorts in a two million franc robbery, in which Pelletier killed a man, then disapppeared with the money. David orders him out, but before leaving, Sarrou says that Pelletier suffered a powder burn on his hand when he committed the murder. David sees a scar on his left hand and begins to suspect that he is Pelletier. The next day, Michele comes to see David at his office and, talking to him as if he were Pelletier, begs for forgiveness and warns him about Sarrou. As she leaves, she shows David a locket with a picture of the two of them together. Later, Michele comes to see David and Lucienne at their home and tries to show Lucienne the locket, but David intervenes and tells his worried wife that Michele had merely come to apologize for her "mistake" at the trial. Soon David receives a 1922 newspaper headline reporting the robbery of which Sarrou spoke. David then goes to see Michele and confronts her, saying that he does not believe Sarrou's story, but she angrily suggests that he go to a certain address and see Pelletier's impoverished mother. David goes to the old woman, who says he is not her son, but her affectionate demeanour deeply moves David, who now ponders the fact that he could have been a thief and murderer in his former life. The next day, Lucienne visits Tessier and voices her concern for David, but says that if David were Pelletier, she would still love him. Suspecting that Sarrou is a blackmailer, she considers using her own jewels and money to buy him off. The next day, Sarrou shows up at David's club, and reveals that Tessier came to see him. Sarrou then demands his money and says that David must bring it that night or the police will be contacted. David goes to Tessier, who reassures him that who he is now is only thing that matters. After wandering the streets, David goes into a travel agency and buys a single ticket to Saigon. That evening, David sends Lucienne alone to a party at the home of his superior, Deval, saying that he has to help a colleague. After she leaves, David gets a call from Sarrou, who knows about the Saigon ticket, and threatens him. Meanwhile, at Michele's place, it is revealed that "Mme. Pelletier" is really De Luc's wife and a former actress. She leaves before the arrival of David, who protests to Sarrou that he does not have one million francs. Then, after David says that it is difficult for him to handle large sums of money at the office, but not be able to use it, Sarrou suggests that they get the money from the office safe and make it look like a robbery. Meanwhile, at Deval's, Lucienne sees the colleague with whom David was supposed to be working and realizes that he has lied. She leaves, and noticing David and Sarrou on the street, follows them to the office. After David tampers with the buildings lights, Sarrou is able to sneak past the guard and takes the money when David opens the safe. Lucienne then arrives and begs David not to go through with the plan, but Sarrou threatens them and suggests that she help him tie David up to make the robbery appear more realistic. Just then, the police arrive and arrest them. At police headquarters, David admits that he is Pelletier and, when Michele is brought in, he begs her and Sarrou to join him in confessing their past crimes. Now faced with being charged as an accomplice to murder, Michele confesses that the real Pelletier died in the train wreck and that she and Sarrou had waited for years to blackmail David, knowing of his amnesia. David then reveals to Lucienne that he finally deduced that the story was a lie when he studied the picture in the locket and realized that it showed his hair as he combed it after the train wreck, parted to cover up a scar. When Deval, who, like the police, was in on David's ruse, reveals that David has just gotten his ambassadorship, David and Lucienne happily embrace.