The Andrews Sisters take a hiatus from show business to aid the war effort. They take on jobs at a pipe-organ plant now making artillery shells. But they still find time for plenty of singing and dancing.

With the outbreak of World War II, the Chadwick Pipe Organ Company, under the leadership of the founder's grandson, Jonathan Chadwick, converts to the manufacture of shell casings. For the company's fiftieth anniversary party, company executive Sparks convinces Jonathan to rent the Four Leaf Clover nightclub. Jonathan, however, embarrasses himself when he undresses nightclub singer Linda Lane during her performance, unaware that the strip-tease is part of her act. In order to help the war effort, many of the nightclub's performers, including the Andrews Sisters, go to work on the assembly line at the new munitions plant. Linda, however, is hired by Sparks as Jonathan's new secretary, though she has no practical experience for the job. Jonathan's problems with Linda continue when she becomes part of his carpool, which has a flat tire its first day. After getting knocked unconscious by a gas station attendant during an argument over a tire, Jonathan is taken back to the nightclub performer's apartment building. Later, when the Four Leaf Clover's new band fails to appear, Linda and her friends, along with Jonathan on piano, act as fill-ins. The next morning, the Chadwick board members decide to sell the company to the Caldwell Company of Pittsburgh, after Sparks informs the board that Jonathan's retooling of the plant has been a failure, as all the shell casings are defective. Later, Linda learns from some of the factory workers that Sparks's assessment of the situation is false, and that the shell casings are in perfect condition. While her friends take Jonathan to the local carnival, Linda goes out on a date with Sparks, during which the executive makes a few remarks that cause Linda to become suspicious. Linda then convinces Jonathan to inspect the shell casings himself, and by checking their tonal qualities, he discovers that they are perfect. Jonathan then stops the sale of the plant to the crooked Caldwell, who was actually working in partnership with Sparks. Believing that Jonathan has no romantic interest in her, the heartbroken Linda decides to take a singing job in New York City, much to the dismay of her friends. During the company's anniversary party, Linda's friends, Monk and Steve, tell Jonathan of her plans, so the industrialist informs Linda that she cannot quit her job because it is vital to the war effort. He then confesses his true feelings for her.