The Apartment

C.C. "Buddy Boy" Baxter is a lonely office worker at Consolidated Insurance Company in New York City. To climb the corporate ladder, he allows four managers to take turns borrowing his Upper West Side apartment for extramarital affairs. Baxter meticulously juggles the "booking" schedule; the steady stream of women convinces his neighbors he is a playboy.
In a quid pro quo, the four managers submit glowing performance reviews of Baxter to personnel director Jeff Sheldrake, who grows suspicious of Baxter's popularity. Under Sheldrake's cynical questioning, Baxter confesses the arrangement with his apartment. Sheldrake implies that he will promote Baxter, if Sheldrake also gains use of the apartment for his own affair, starting that night. As compensation for short notice, he gives Baxter two tickets to see The Music Man. Baxter asks Fran Kubelik, an elevator operator coworker to whom he is attracted, to join him. She agrees to meet Baxter after dinner with a "former fling", who turns out to be Sheldrake. When Sheldrake tells her that he plans to divorce his wife to be with her, they head to Baxter's apartment, while Baxter is stood up at the theater.
During the company's raucous Christmas Eve party, Sheldrake's secretary, Miss Olsen, tells Fran that her boss has had numerous affairs with female employees, including herself. Fran confronts Sheldrake at Baxter's apartment; he claims he loves her, gives her $100 as a Christmas present, which makes her feel "paid", and heads back to his family in White Plains.
Realizing Fran is the woman Sheldrake has been taking to his apartment, Baxter lets himself be picked up by a married woman at a local bar. When they arrive at his apartment, Fran is passed out on his bed from an overdose of sleeping pills. He sends away the woman from the bar and enlists his neighbor, Dr. Dreyfuss, to revive Fran. To deflect questions and protect Sheldrake, Baxter implies he was responsible for the incident; Dreyfuss scolds him for philandering and advises him to "be a mensch."
Fran spends two days recuperating in Baxter's apartment. A bond develops between them, especially after he confesses to a comically botched suicide attempt over unrequited love where he shot himself in the knee. Fran confides she has always suffered bad luck in her love life.
As Baxter prepares a romantic dinner, one of the managers arrives for a tryst. Baxter persuades him and his companion to leave, but the manager recognizes Fran and later informs his colleagues. They are annoyed they have lost ready access to the apartment since Baxter's promotion. When Fran's brother-in-law Karl comes to the office looking for her, the managers send him to Baxter's apartment. Baxter deflects Karl's anger over Fran's wayward behavior by once again assuming all responsibility; Karl punches him. As she leaves, Fran chides Baxter for taking the blame but kisses him for protecting her.

When Sheldrake learns Miss Olsen told Fran about his affairs, he fires her; she retaliates by spilling all to Sheldrake's wife, who promptly throws him out. After complaining to Baxter that women expect affairs to lead to marriage, Sheldrake gives Fran insincere assurances; she now hints she is losing interest. Having promoted Baxter to an even higher position, Sheldrake expects Baxter to resume lending the key to his apartment so he can take Fran there. Instead, Baxter gives back the key to the building's "executive washroom", proclaiming that he has decided to become a mensch, and quits the firm. He decides to move out of the apartment and begins to pack his belongings.
That night at a New Year's Eve party, Sheldrake indignantly tells Fran about Baxter's quitting, disclosing that Baxter refused to let him use his apartment, particularly with Fran. She abandons Sheldrake and runs to the apartment. At the door, Fran hears an apparent gunshot, but Baxter opens the door holding a bottle of just-opened champagne. Baxter declares his love for Fran. As she prepares to resume a game of gin rummy left unfinished earlier, she smiles, hands him the cards and says, "Shut up and deal".