Set in the 6th Century, this is the story of twin brothers David and Thomas and their sister Freya who discover a plot by King Arthur's sister (Morgana) to kill all the dragons in the kingdom and, with the aid of her co-conspirator Aelle, a Saxon king, to kill her brother to become Queen. Banding with the dragons and some local people the siblings join King Arthur in his battle. During the fighting David is injured with a poisoned spear thrown by a Death Rider. Merlin immediately sends them to find the cure. This quest takes them far from home and through strange and dangerous lands where they once again encounter Morgana and the Death Riders.