1261. Oxford, England. An envoy returns from the land of the Tartars to meet with an English scholar and share a deadly secret. The two men vow that the knowledge of gunpowder must die with them as the consequences are otherwise too fatal to contemplate.

1290. Hurnwych Green, England. After his quiet life is shattered by tragedy, blacksmith Jared begins a pilgrimage to the Promised Land. Along the way he is invited to join the Knights Hospitallers as their blacksmith on a holy crusade for King Edward. The adventure that follows sees Jared encounter men from distant Cathay who harbour the secret of huo yao, and so begins one man’s obsession with the powder of death and a king’s determination to change the very nature of warfare.