When an ancient helmet at the British Museum is taken, Bridgette and Duncan are confronted by another hero of yore, one who will lead them to facing off against their most formidable challenge yet...a beast and his mother.

Although Bridgette and Duncan stopped Arthur from retrieving the Grail and separated him from the legendary scabbard of Excalibur, the undead King of the Britons still has his sights on returning to our world and returning to power. By inadvertently changing the story of the famous King, Duncan and Gran have thrown the Otherworld into shambles, allowing for new legends and characters to make their appearance - and bring a world of trouble along with them.