In 1942, with the Second World War at its height, a US naval crew intercept the distress call of a disabled German submarine, U-571, and board the vessel posing as a rescue party. On board they discover the top-secret Enigma de-coding machine, but before they can return to their own craft it is torpedoed by a genuine German rescue sub. The Americans are forced to flee in U-571, taking with them a solitary German prisoner. As they make their way through an Atlantic ocean teeming with enemy ships, the US navy crew begin to realize that their enemy is always one step ahead of them...