During Danny Xavier Smith and Rico Ferrari's Arctic duty at a U.S. Navy reservation nicknamed "Operation Ice Cream," their friend Bill recruits them to bake a birthday cake for the commander. Bill explains that a planeload of replacements is due, and if they can impress the commander with the cake, they might be sent home. Left alone in the kitchen, the two friends admit they have no idea how to bake, so they hatch a reckless plan: sabotage a rival sailor’s failed cake, fill its hollows with rum, and decorate the whole thing with candles and icing. The commander is delighted—until the cake explodes when the candles are blown out, and the trio is reassigned to a new, even riskier mission: "Operation Mud Pie" in a swamp crawling with snakes.
Two days later, on shore leave in San Francisco, Bill visits the nightclub where his fiancée Ginger is the star. Ginger, tired of a six-year engagement, confesses she has fallen for someone else and ends things. Meanwhile, Mrs. Ferrari, Rico's widowed mother, hosts her blossoming household and entertains her beau, florist Mr. Peroni. Peroni had previously assumed Rico was a child, and that mistaken belief now colors his interactions with Mrs. Ferrari, sparking a new tension in their relationship. Danny heads to see his father, Rear Admiral Daniel Xavier Smith, while his sister Susan Smith reveals she’s dating actor Wendell Craig and may land a part in his latest show.
Back at the theater district, Danny is drawn to the glamorous dancer Carol Pace during rehearsals for Wendell Craig’s production, Hit the Deck. Carol warns Danny that Wendell is a notorious womanizer, which makes him worry for his sister’s safety. Meanwhile, Bill returns to Ginger and presses for a wedding date, but the tension remains. In Wendell’s hotel suite, Susan Smith performs for him, and the lecherous actor makes a move just as Danny and his friends crash the scene. Rico forcibly escorts Susan home and finds himself falling for her. Susan slips away and, after returning to the hotel, encounters Rico in the hallway, deciding they must warn Danny and Bill.
The shore patrol questions Ginger at the nightclub, but she refuses to divulge anything about the sailors’ whereabouts. The group—Susan, Carol, Ginger, and Mrs. Ferrari—congregates at Mrs. Ferrari’s apartment, where they try to keep spirits up with wine and song. The Admiral returns early and learns that Danny is in trouble; the next morning, the shore patrol resumes their search, and Mrs. Ferrari delays them while the men seek refuge in Mr. Peroni's flower shop. To stir Peroni’s jealousy, Rico has Bill pose as Mrs. Ferrari’s new suitor and sends roses to the florist. Peroni personally delivers the flowers and, moved by the gesture, asks Mrs. Ferrari to marry him—an invitation she happily accepts.
Bill then visits Ginger again and finally proposes, adding another layer of romance to the upheaval. That evening, just before Hit the Deck’s curtain rises, Wendell tries to cover the bruises on his face with makeup, and Susan begs him to drop the charges. He agrees, but only if the sailors publicly apologize in person; Susan goes to fetch them, and Wendell picks up the phone to stall. When Susan returns with the three sailors to Wendell’s dressing room, they find the shore patrol waiting. The men flee, slipping into the chorus in sailor garb as the admiral and Lt. Jackson watch in astonishment from the audience. A scuffle erupts during the opening number, and Susan punches Wendell in the heat of the moment.
The sailors are captured and brought before the admiral, who chastises them until he learns that the young woman they defended is Susan. After the confrontation, Mrs. Ferrari bursts in, followed by Carol and Ginger, who back up the trio’s version of events for Lt. Jackson. The admiral goes home to confront Susan, who suggests she might marry Rico, while Lt. Jackson arrives with Wendell, who now claims the charges were a misunderstanding and withdraws them. In the end, the three sailors are joyfully united with their loves, and the tangled relationships settle into a hopeful, celebratory close.
