April 1942: Hitler's U-Boats are wreaking havoc in the Atlantic and destroying Allied shipping up and down the United States' East coast. Unable to crack the U-Boat radio codes, the U.S. struggles blindly against the German onslaught -- that is until the crew aboard the S-33, a vintage World War I submarine, is assigned a dangerous mission that, if successful, will have the power to turn the tide of battle permanently. Led by Commander Mike Dahlgren and Lt. Andrew Tyler, the S-33 crew is ordered to capture Enigma, the German's top-secret coding device. To bait the Germans, the S-33 is rigged to resemble a stranded Nazi U-Boat. If all goes according to plan, the crew will take the Germans as prisoners and steal Enigma -- if the plan fails, nine U.S. soldiers will be trapped in a submarine in the middle of hostile, enemy waters with little or no chance of survival.