Four days before Christmas 1943, a badly damaged American bomber struggled to fly over wartime Germany. At its controls was a 21-year-old pilot. Half his crew lay wounded or dead. It was their first mission. Suddenly, a sleek, dark shape pulled up on the bomber’s tail—a German Messerschmitt fighter. Worse, the German pilot was an ace, a man able to destroy the American bomber in the squeeze of a trigger. What happened next would defy imagination and later be called the most incredible encounter between enemies in World War II.

Ultimately, Charlie and Franz would stare across the frozen skies at one another. What happened between them, the American 8th Air Force would later classify as “top secret.” It was an act that Franz could never mention or else face a firing squad. It was the encounter that would haunt both Charlie and Franz for forty years until, as old men, they would search for one another, a last mission that could change their lives forever.