March 1943. Two Allied convoys, HX.229 and SC.122 leave North America bound for Britain. They total nearly 100 ships carrying vital food and raw materials to supply the Allied war effort. Lt. Commander John Gordon Luther commands the escort group charged with protecting convoy HX.229. Short at least two ships, he lacks adequate defenses for the mid-Atlantic U-boat attack that the Karl Donitz, Gross Admiral of the German Navy, has in store for them.
For three days the convoys are hammered merciless by an Atlantic winter storm and torpedo attacks. Many ships are hit and Luther is repeatedly torn between protecting the convoy or falling back to rescue survivors. It’s the largest convoy battle of the Second World War and one that brings the Allies perilously close to losing the Battle of the Atlantic.