While his son is comatose from an ecological accident, Derek Wythin becomes obsessed with vivid dreams that he begins to believe are depicting one of his Arthurian-age ancestors. He must somehow enable this ancestor to survive in the past or Derek will cease to exist in the present. But perhaps his mind is betraying him, as he also fights to meet the challenges of his modern world and not be taken over by a menace lurking in his subconscious.