An American artist finds love in Paris but almost loses it to conflicting loyalties.

American Jerry Mulligan, a former G.I. and fledgling painter who stayed in Paris after World War II, loves his life as a struggling artist on the Left Bank. He is friendly with his neighbors, especially the local children and cynical American Adam Cook, a concert pianist living on a succession of fellowships. One day, when Jerry is particularly low on money, he goes to Montmarte and sets up an impromptu exhibit of some of his work, hoping to sell something to a tourist. He has little success until Milo Roberts, an American heiress living in Paris, admires his paintings and buys two. Because she does not have enough cash with her, she invites Jerry to her hotel to get the money. Jerry shows little enthusiasm for her chauffeur-driven car and expensive hotel room but accepts an invitation to a party she is giving that night. When he returns, the provocatively dressed Milo reveals that the party is only for herself and Jerry. Thinking that she wants a gigolo, Jerry is insulted and wants to return the money for his paintings, but she convinces him that she is a patron of the arts and only wants to help him. With his pride intact, Jerry agrees to take her to dinner, but only if they go to a café he can afford. She suggests a jazz club in Montmarte, where they talk about their lives and his paintings. While Milo dances with Tommy Baldwin, a friend she runs into at the club, Jerry, who is attracted to a pretty girl he has spotted at the next table, overhears her name, Lise Bourvier, and calls to her, pretending to know her. After whisking the annoyed Lise onto the dance floor, Jerry gets her phone number from one of her companions. Observing this, Milo is hurt and lashes out at Jerry while they drive back to her hotel. He responds by getting out of her car and determining he wants nothing to do with her. The next morning, Jerry telephones Lise at the perfumery where she works and asks her out. She brusquely turns him down and tells him not to call again. A few moments later, Milo shows up at the Flodair, Jerry's neighborhood café, and apologizes for her outburst the previous night. Again insisting that she is only interested in promoting his work, she invites him to lunch to meet a well-known art dealer she knows. Jerry agrees to meet her later, then goes to the perfumery to see Lise. When he charms a middle-aged American customer into selecting a perfume, Lise is amused and agrees to meet Jerry at 9:00 o'clock that night at a café near the Seine. Unknown to Jerry, Lise is loved by popular music hall entertainer Henri Baurel, a close friend of Adam and the man who became her guardian when her parents were killed during the war. Henri is debuting a new number that night and wants Lise to be in the audience. Although Lise is torn, she meets Jerry that evening, and as they walk along the Seine, the couple begins to fall in love. When Lise suddenly realizes that it is 11:00, she rushes off after agreeing to meet Jerry again on Saturday. At the theater, Henri does not realize that Lise missed the number and introduces her to American impresario John MacDowd, who wants Henri to tour America. Assuming that Lise loves him as much as he loves her, Henri suggests that they get married and go together to America. The next day, when Milo calls for Jerry, he dismisses Adam's suggestion that he is becoming a kept man. Later, when Milo takes Jerry to a studio she has rented for him and informs him that she has arranged for an exhibition, he is angry but agrees to work hard if she promises to let him pay her back for everything. For the next few weeks, Jerry paints constantly, highlighting the people and sights of Paris, often using Lise as his model. One day, while Lise and Jerry are riding in a taxi, they talk about how little they know about each other's lives and realize that they have both been evasive. Later, at the Flodair, Jerry tells Adam about Lise, and when he mentions her name, Adam chokes on his coffee, knowing that she is the young woman whom Henri loves. When Henri arrives, he and Jerry talk about being in love while Adam nervously tries to change the subject and hopes the men will not mention the names of their respective loves. Henri convinces Jerry that he must tell his girl friend how much he loves her, so when Jerry later meets Lise, he reveals his feelings. Although she feels the same, Lise confesses that she is marrying Henri because he loves her and she owes him her life. Hurt, Jerry then says that he has been seeing a woman he does not want to lose. After they part, Jerry rushes to Milo's apartment, passionately kisses her for the first time and asks her to the art student's costume ball that night. At the raucous ball, Jerry dances with Milo, pretending that he is happy, but after they run into Henri and Lise, Jerry admits to Milo that he is in love with Lise. Milo then leaves, after which Jerry walks out onto the balcony, where he is joined by Lise. She says that she and Henri are marrying the next day, but before returning to the party admits that it is painful to be near Jerry and not hold him close. Unknown to Lise and Jerry, Henri has been smoking a cigarette near by and has overheard everything. Without saying a word to Lise, he drives her from the party while a despondent Jerry fantasizes about Lise and imagines himself dancing with her throughout Paris. A short time later, he is startled to hear the horn of a car and looks down to see Lise being brought back in Henri's car. While Jerry runs down the Montmarte steps, Lise rushes up to meet him. The lovers embrace and walk down the steps hand-in-hand.