When an ancient sword is found beside a Somerset lake, the insurance company engages archaeologist Dr Jeffrey Flint to investigate whether this really is Excalibur, the fabled blade of King Arthur.
Convinced the sword is a fake, Flint is confronted by a bizarre academic conundrum where death is always lurking beneath the surface. With the aid of his tenacious assistant, Tyrone Drake, Flint follows a trail which weaves in and out of English folklore.
Where ancient legends are met by relentless media hype, a conspiracy takes shape, and tragedy soon surrounds the mystery of the lady in the lake.