The crews of HMS submarine Sea Tiger have their leave (and assorted family problems) cut short when they are recalled for a special mission: sink the new German battleship Brandenburg. En route, they learn that their target has entered the heavily defended Baltic; rather than fail, they follow it. Tension builds as they approach their target. After the attempt, escape seems impossible…unless they can refuel in enemy waters. Very realistic depiction of submarine action especially considering the filming of this motion picture took place during WWII.