London, Autumn 1916. When he slips out of a house in the early hours of the morning, Simon Wilder is too preoccupied to realise that is being stalked. As he walks along the street, lights begin to dim as a warning that there's another Zeppelin attack. Guns begin to pound away as British aeroplanes attack the Zeppelin. Suddenly, it bursts into flame and lights up the whole sky. The crowds cheer as the great fireball drops slowly down and crashes in a field but the one person unable to watch is Simon Wilder. While he is staring up at the sky, he is stabbed to death and left in an alleyway. It will prove to be a very puzzling case for Inspector Marmion and Sergeant Keedy...