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.