A traitor is lurking somewhere aboard the USS Carolina, and Lt. Tom Randolph (Robert Taylor) is determined to find the offender. First a revolutionary new piece of technology -- an electric firing device -- is sabotaged. Then one of the cruiser's crew is murdered. In order to catch the killer, the captain locks down the ship. With foreign dignitaries, corporate goons and even Tom's girlfriend, Betty (Jean Parker), trapped on the vessel, there is no shortage of suspects.