In March 1941, after a year of unbroken and devastating U-boat onslaughts, the British War Cabinet decided to try a new strategy in the foundering naval campaign. To do so, they hired an intensely private, bohemian physicist who was also an ardent socialist. Patrick Blackett was a former navy officer and future winner of the Nobel Prize; he is little remembered today, but he and his fellow scientists did as much to win the war against Nazi Germany...