Kaperski kapitan marynarki wojennej USA i jego załoga dopiero zaczynają 48 godzin urlopu, gdy dostają rozkaz natychmiastowego powrotu do duty. Na tajnej misji muszą się przebrać za nazistów i infiltrate severely damaged Nazi U-boat. Once on board, they are to steal the Nazi's top-secret decoding device and sink the sub before the Germans catch on to what's really happening. Their mission is more dangerous and frightening than anything they could have ever imagined, but one which has the power to turn the tide of battle.