The year is 1914 and Europe, armed with futuristic machines and biotechnology, is on the precipice of war. Prince Aleksandar is fleeing for his life, having discovered that his parents have been assassinated and that he is now a target for the Clanker Powers, a group determined to take over the globe with their mechanical machinery. They will stop at nothing to get what they want, so Alek knows his only choice is to keep on running. When he meets Deryn Sharpe, an orphan girl who has disguised herself as a boy so she can to join the British Air Service, they form an uneasy, but necessary, alliance. But the pair will soon discover that their emerging friendship will dramatically change their lives and the entire course of the Great World War...