Cmdr. Richard Bolton (James Caan) was in charge of a submarine that was sunk by a German ship, and he has been blamed for the loss of 50 sailors. Now exonerated of misconduct, he is heading a mission to use minisubs to reach a German battleship commanded by Capt. Erlich (George Pravda). During training, Bolton encounters some of his previous crew members, all of whom harbor grudges against him, which further complicates the already dangerous mission.