Hereward discovers a buried sword and realizes it has extraordinary power, but what he doesn't realize is that this sword is Excalibur and that his life is now in grave danger. There are traitors all around - people who want Excalibur so they can claim the throne of England. Ursus and Gwyneth must make Hereward see that the treasured sword has to be returned to its burial place - until the time is right for it to be found again . . .