Thanks to his father's gambling debts, young Jack Keats finds himself on the streets and trying to survive as a pickpocket, desperate to graft enough coins to keep him and his sister fed.
Inevitably, Jack is arrested and pressed into Royal Aerostatical Navy, where he finds himself assigned to the most useless airship in the fleet, manned by the assorted scrapings of poorhouses, prisons and the press gang. Serving under a captain who is most probably mad, Jack seems to be bound for almost certain death in the far-away deserts of Cassarabia.
Meanwhile, on the other side of the world, Omar Akil, the favoured servant - and some say bastard son - of a rich merchant lord finds his life turned upside down when his master's religious sect is banned. He narrowly escapes the death sentence by entering into the service of the Caliph's military forces -- just as war is brewing.
Two very similar young men prepare to face each other across a senseless field of war. But is Omar the enemy, or is Jack's true nemesis the sickness at the heart of the Caliph's court? A cult that hides the deadly secret to the origins of the gas being used to float Cassarabia's new aerial navy.
If Jack and his shipmates can discover what Cassarabia's aggressive new regime is trying to conceal, he might survive the most horrific of wars and clear his family's name. If not...