Young socialite Gladys Witham begins working at Victory Munitions, a bomb factory, at the start of World War II. Taking a job as a secretary during the factory's Blue Shift, Gladys arranges to become a floor worker instead, after being inspired by the other women floor workers. Kate Andrews, also a newcomer, has begun working at the factory after running away from her abusive father; she is reluctantly taken under the wing of Betty McRae, the factory's best worker. Blue Shift floor matron, Lorna Corbett, clashes with Marco Moretti, an Italian-born worker at the factory. Meanwhile, Vera Burr is severely injured while working on the assembly line, and ends up in the hospital.