It's 1941, and German Gen. Erwin Rommel and his armies hope to take Egypt, gain control of the Suez Canal, and prevent Britain from receiving vital supplies from the colony of India and the Middle East. The Allies' last line of defense is a fleet of small, British Royal Navy U-class subs stationed on the tiny island of Malta. Despite unpredictable weather and a broken gyrocompass, HMS Upholder and its Lieutenant-Commander Malcolm Wanklyn hunt Italian supply ships to hold the line against the Axis powers and turn the tide of the North African Campaign.