Sub-lieutenant Paul Everard serves aboard the submarine Ultra in the Mediterranean where the Allies keep up their desperate attacks against Axis supply ships. But Paul has other troubles as well: his father, Nick, is somewhere in the Far East where Japanese superiority continues to pound the Allies, and his brother, Jack, now enmeshed in the murky world of clandestine operations, has been sent on a high-risk mission to destroy a key German naval base.