Follows the daring patrol of the U-96, one of the famed German U-boats known as the "gray wolves." The crew is graphically portrayed in a life-and-death struggle, challenging the British Navy at every turn.

During World War II, a group of Navy men are sent to steal Enigma (the nazis' top-secret decoding device). When their own ship is destroyed, they must secretly make their way through hostile waters in a severely damaged Nazi U-boat to safety with the device.