During World War II, in the summer of 1940, Winston Churchill faced a terrible dilemma. France had just surrendered and only the English Channel stood between the Nazis and Britain. Germany was poised to seize the entire French fleet, one of the biggest in the world. With these ships in his hands, Hitler's threat to invade Britain could become a reality. Churchill had to make a choice: to either trust the promises of the new French government: that they would never hand over their ships to Hitler; or he could ensure that the ships never joined the German navy by destroying them himself. His decision is regarded by some as a turning point in the war, while others call it a terrible betrayal and a war crime. This documentary tells the story of what Churchill did next, and how and why 1300 French sailors died as a result in what the French still call their Pearl Harbor. The filmmakers interview French survivors who were aboard the targeted battleships, and also a British war veteran, a sailor who opened fire on his former allies. Along with these fist-hand accounts, historians and Churchill's biographer trace the chain of events and their consequences for those involved, for Britain and the outcome of the war. This is the forgotten story of Churchill's darkest decision: to sink the French Fleet.