The D-day landings - the fate of millions of men and the entire future of Europe depends on the right weather conditions on the English Channel on a single morning. A team of Allied scientists is charged with agreeing on an accurate forecast five days in advance. But is it even possible to predict the weather so far ahead? Will Wallace Ryman, reclusive pacifist and renowned forecaster, divulge his secrets to the team? Can Henry Meadows, a young maths prodigy, save the day? Or will turbulence prove even more elusive than imagined and events, like the weather, begin to spiral out of control?