Spring 1917. The average survival time of a First World War reconnaissance pilot is eighteen hours. After weeks in the thick of it, George Duckwell, reluctant novice-hero of the Royal Flying Corps, is living on borrowed time, watching in horror as a succession of comrades are shot down, burned, maimed and killed, while somehow he survives. Struggling to make sense of the conflict, George forms an awkward friendship with William 'Mac' MacBride, an enigmatic Canadian ace, waging his own private war against the legendary Red Baron, Manfred von Richtofen. But when Mac falls for George's sweetheart - front-line nurse Emily - the fragile bond that keeps the two men alive comes under threat on the eve of the most lethal conflict the modern world has known.