The untold story of the D-Day scientists who changed special operations forever.

On the beaches of Normandy, two summers before D-Day, the Allies attempted an all but forgotten landing. Of the nearly seven thousand Allied troops sent ashore, only a few hundred survived the terrible massacre, and the reason for the debacle was a lack of reconnaissance. The shore turned out to be impassable to tanks. The Nazis had hidden obstacles in unexpected places. The fortifications were more numerous – and deadly – than imagined. The Allies knew they needed to take the fight to Hitler on the European mainland to end the war, but they could not afford to be unprepared again. A small group of eccentric researchers, experimenting on themselves from inside pressure tanks in the middle of the London air raids, explored the deadly science needed to enable the critical reconnaissance vessels and underwater breathing apparatuses that would enable the Allies' dramatic, history-making success during the next major beach landing: D-Day.