Writer Georges Duroy (George Sanders) is one social-climbing S.O.B. who does most of his climbing over the warm (and cold) bodies of women. He begins with Rachel (Marie Wilson), a hanger-on in the cafes and Folies Bergere crowd, and then moves on to dally with Clotilde de Morelle (Angela Lansbury.) Always striving to move upward on the social scale, he ditches her to marry Madeleine Forestier (Ann Dvorak). Now he gets on the fast track. He persuades Madame Walter (Katherine Emery), the wife of his publisher, to fall in love with him, and then compromises Madeleine to frame a divorce, so he can pursue Madame Walter's daughter, Suzanne (Susan Douglas, before somebody decided her later-married name was her most-often used screen name.) He moves along so well that ere long he is in legal position to usurp the title of one of France's most noble houses. The moral, at the end, is it is okay to mess with French women, but triffling with French titles is going too far.

In a Paris sidewalk café in 1880, ex-soldier Georges Duroy meets an old army comrade, Charles Forestier, who offers to get him a job at a newspaper owned by Monsieur Walter, an aristocratic tycoon. During a dinner party at Charles' home the following evening, Georges is introduced into Paris society by Charles' beautiful wife Madeleine. Among the guests is Madeleine's best friend, Clotilde de Marelle, a young widow and mother of a young daughter named Laurine. Over dinner, Georges and the other guests discuss the puppet "Punch," a self-serving, brutish character with whom Georges has long been fascinated. Blind Norbert de Varenne, an organist at Notre Dame cathedral, poignantly interjects that those who are puppets of the devil are not themselves to blame for their exploits. The ambitious Georges then quickly ingratiates himself with Monsieur Walter. Later, with Madeleine's help, Georges starts a gossip column called "Echoes," through which he hopes to manipulate the social and financial pillars of Paris. At the same time, Georges and Clotilde fall in love. One night, however, Clotilde learns at the Folies Bergère that Georges has been involved with a young dancer named Rachel and realizes that he will never be faithful to her. Charles later dies from tuberculosis, and Georges marries the widowed Madeleine. Georges tells Clotilde that the marriage is merely one of convenience, and that he will always love her. Georges soon finds it advantageous to seduce Monsieur Walter's unhappy, aging wife, who falls desperately in love with him. One day, she confesses to Georges that Monsieur Walter and Georges' nemesis, political editor Laroche-Matheiu, are plotting to use Georges' column to make a profit in the stock market and agrees to lend him money to get in on the deal. As she then talks about a dream she had about him, Madame Walter tenderly winds strands of her hair around his coat button. When he stands, Georges callously rips the hairs from her head. Clotilde later finds the strands on his button and chastises him for deceiving Madeleine. The Count de Vaudrec, an elderly admirer of Madeleine, then dies, leaving his considerable fortune to her. As Madeleine's husband, Georges must by law approve her inheritance before she can accept the money, and he interrogates her about her relationship with the count. Although Madeleine swears that de Vaudrec was like a father to her, Georges insists that half of the inheritance be put in his name for appearance's sake. He then asks Madeleine to befriend Laroche-Mathieu, who is now the Minister of Finance, so that he can learn his secrets. One afternoon, while Madeleine and the minister meet, Georges sends a lawyer to accuse them of adultery, knowing the accusation will ruin Laroche-Mathieu's career. After Georges divorces Madeleine and takes half her fortune, he immediately begins a secret courtship with the Walters' daughter Suzanne, who stands to inherit forty million francs. He needs a title to marry her, however, and believing that there are no living descendants of the de Cantel family, applies for the family's three-hundred-year-old title. Now a man of nobility, Georges asks Monsieur Walter for his daughter's hand. The news of her daughter's engagement shocks the madame into a stupor, and she spends her days staring at "The Temptation of Saint Anthony," a painting she has recently acquired. Plotting her revenge, Madame Walter sends a clipping of the public notice for the title to a farmer in the de Cantel region, hoping a de Cantel descendant will step forward. Before the wedding, a man named Philippe de Cantel comes to Paris to challenge Georges to a duel. On the morning of the duel, Georges tells Clotilde that he has left his fortune to her and Laurine--the only two people he ever really loved. She races to the Walters' home to beg Suzanne to marry Georges without the title, and together with Madame Walter, they rush to the Bois de Vesinet, where the duel is to take place. After taking ten paces forward, Philippe is shot in the stomach by Georges, and has two minutes to return fire. Crawling in agony toward his opponent, Philippe shoots Georges in the chest just as the women arrive. As Georges lies dying in a carriage, Madame Walter defiantly informs him that it was she who notified Philippe. Before he dies, Georges wistfully murmurs that he could have been happy with Clotilde.