"Baxter" (Jack Lemmon) has devised an unusual scheme for career advancement. He rents out his apartment each evening to his superiors so they can entertain women, all with the expectation of a promotion from his $90-a-week position. This often leaves him waiting outside in the cold while they consume his alcohol supply. Promises are made—more promises—but will he ever land that better job? His only source of enjoyment is the enigmatic but cheerful elevator operator "Fran" (Shirley MacLaine), though it becomes clear she’s involved with another high-ranking executive. It's this man, "Sheldrake" (Fred MacMurray), who has the power to help “Baxter,” but at what price? He comes across as somewhat of a heartless character, casually manipulating "Fran’s" feelings. Eventually, she becomes deeply disheartened and takes extreme measures that fortunately our hero manages to prevent. With her still shaken and upset, the stage seems set for a fairly standard resolution. This isn't among my most cherished Billy Wilder films. I thought the initial thirty minutes leaned too heavily into an almost overly clever style of humor, and while I appreciated his work, I couldn’t connect with Jack Lemmon’s character. MacLaine and MacMurray, however, offered characters who elicited both sympathy and disdain in equal measure. The writing demonstrates what can be achieved without relying on crude language, yet still effectively conveys feelings of aggression, frustration, and yes—even affection. It's all set during Christmas, which proves quite useful as it highlights the many hypocrisies that surface around this time of supposed "good will." The supporting actors also perform well, particularly his neighborly doctor (Jack Kruschen) and wife (Naomi Stevens), who believe he’s constantly having affairs next door. Ultimately, it's driven by three strong performances delivering a concise and touching script that should warn you never to hand over your spare key to anyone.

Source on TMDB