Dick Young stays in his friend Professor Magnus Lane's house in Cornwall, on the understanding he will be a guinea-pig for a new drug that Magnus has developed. As a result of the experiment he is transported back to fourteenth century Cornwall. With each 'trip' he becomes more and more involved with medieval intrigue, adultery and murder. Is it merely hallucination; a subconscious escape from his own complicated life, or a real journey into the past? He becomes obsessed with the world he visits, and past and present eventually become inextricably and perilously mixed.