At Norfolk Naval Base in the opening months of World War II, Lieutenant John W. Harkness (Cooper), a newly commissioned officer, bids goodbye to wife Ellie (Jane Greer) and reports aboard the "PC-1168" unaware that his civilian background in engineering and his Rutgers education has elected him, by means of a hole punched in an IBM card, to head a secret project and command the ship. The Navy has installed a steam engine and an experimental evaporator-condenser in the ship to test its feasibility in patrol craft and has assigned Harkness to conduct the sea trials.