An envoy to China meets an English scholar in Oxford in the mid-thirteenth century to share a deadly secret. They vow that the knowledge of gunpowder must die with them as the consequences otherwise are too terrible to contemplate.
But the secret is rediscovered, one man becomes obsessed with the powder of death and Edward III is determined to use it to his advantage. He does so at the Battle of Crecy, the first full-scale battle at which guns are deployed in the field. The nature of warfare is changed for ever, and the world hears the death knell of knightly chivalry.