It's 1941, and the Society for the Preservation and Encouragement of Barber Shop Quartet Singing in America (S.P.E.B.S.Q.S.A) is holding a competition to find the best Barbershop Quartet in America. The only catch: No Girls Allowed. But with the help of fake moustaches, bad suits, and great voices, a fearless foursome of females turns the singing contest into a hilarious battle of the sexes.