September 1939. The legendary American Flying Clipper, a gigantic flying boat, departs from Southampton on its final flight across the Atlantic. On board the aircraft: forty passengers, including a Jewish scientist, a clever jewel thief, an ultra-conservative lord and his rebellious daughter, a secret agent on a mission, and a manufacturer who is being betrayed by his beautiful wife. Each of them faces the most important decision of their lives. Yet only one knows the looming danger that lurks over the waters...