On the night of December 2, 1943, the Luftwaffe bombed a critical Allied port in Bari, Italy, sinking seventeen ships and killing over a thousand servicemen and hundreds of civilians. Caught in the surprise air raid was the John Harvey, an American Liberty ship carrying a top-secret cargo of 2,000 mustard bombs to be used in retaliation if the Germans resorted to gas warfare. After young sailors began suddenly dying with mysterious symptoms, Lieutenant Colonel Stewart Alexander, a doctor and chemical weapons expert, was dispatched to investigate. He quickly diagnosed mustard gas exposure, which Churchill denied. Undaunted, Alexander defied British officials and persevered with his investigation. His final report on the Bari casualties was immediately classified, but not before his breakthrough observations about the toxic effects of mustard on white blood cells caught the attention of Colonel Cornelius P. Rhoads - a pioneering physician and research scientist as brilliant as he was arrogant and self-destructive - who recognized that the poison was both a killer and a cure, and ushered in a new era of cancer research. Deeply researched and beautifully written, The Great Secret is the remarkable story of how horrific tragedy gave birth to medical triumph.