The battle for the Atlantic was at a peak for the British. Superior German battleships seemed to roam freely wreaking havoc on supply convoys to the allies. When the German battleship Tirpitz is discovered in a Norwegian fjord, the British have no ships available to protect their western supply lines against this heavy hitting menace. The undaunted British come up with a bold plan to use unproven mini subs. These little 4 man submarines didn't deliver a torpedo to their target but instead were designed to deliver explosives that would have to be planted underneath an enemy vessel. Unbelievable courage, skill and determination by three crews of these experimental vessels lead you on a mission like you've never experienced.