Terry Atkinson's study presents a fresh and startling theory about the true origin of one of our most enduring legends - the quest for the Holy Grail. Many authorities agree that the core theme of this seductive story, through all its metaphoric mutations over the centuries, is humanity's unrelenting desire for spiritual transcendence - for a state of heightened consciousness.

Our modern concept of the Grail dates from the 15th Century story of the chalice from Christ's Last Supper, brought to the British Isles and then buried or somehow lost, and the subsequent holy mission of King Arthur's knights to retrieve the icon. But in traditional cultures of past millennia, where the legend originates, the goal of this sacred quest was a religious encounter of a different order. Our ancestors sought to reveal the presence of the divine being within through a mind-expanding experience rooted in nature.

Every version of the Grail legend features near-impenetrable coded references to its entheogenic origins - the ritual use of naturally occurring psychedelics to reach transcendence. Approaching the subject like a detective solving an ancient mystery, the author employs textual forensics to explain for the first time the meaning behind several aspects of the story that have puzzled scholars for centuries.

Unlike such works as Holy Blood, Holy Grail (whose theory was used as the basis of The Da Vinci Code), Atkinson's book delves deeply into Grail literature from the 12th Century, particularly the very earliest written work, Chrétien de Troyes' Parsifal. Launching a detailed investigation of the legend's intriguing fish symbolism and examining the key role of shamanism in Celtic and other ancient cultures, the author also uses clues drawn from Grail scholar Jessie Weston's From Ritual to Romance, the classic study that inspired T. S. Eliot's The Waste Land.

The Grail is more real than most recent explicators and fabricators imagine, but in a very different way from that assumed by the old-school searchers. The author's astonishing conclusion is that the hallucinogenic mushroom Amanita muscaria is the long-lost secret origin of the legend.