On 21 May 1941, Ian Fleming of Naval Intelligence lunches with Aleister Crowley in Mayfair. Crowley has offered to interview Rudolf Hess, who has been captured near Dungavel, the Duke of Hamilton's Scottish estate, eleven days before. Their shared affinity for the occult will enable the Beast to draw out the German's secrets. Fleming agrees and gives the Beast the 1939-41 diary of Albrecht Haushofer, Hess's principal adviser. This gives the background to the deputy führer's flight and describes the involvement of Karl Ernst Krafft, a Swiss astrologer, who has an uncanny knack of making accurate predictions.
On 1 February 1945, Crowley moves to Netherwood, a boarding house in Hastings. Will, the teenage handyman, intends to become a Catholic priest but is distracted by a maid called Maria. Crowley tutors him in Latin. Left alone in Crowley's room, Will stumbles on a file that describes the Beast's wartime encounter with Hess. It is called the 'Z' File, 'Z' being Hess's codename. Crowley has capitalised on his resemblance to Churchill and deceived Hess into believing he is the prime minister. Hess reveals the date of the attack on Russia.
Several visitors come to Netherwood to see the Beast: Dion Fortune; Frieda Lady Harris, creator of the Thoth Tarot paintings; a female Oxford professor researching a book on the characteristics of a magician; John Symonds, his future biographer; and a pupil of Crowley called Maxwell Knight. Knight is, in fact, the spymaster 'M' who runs a division of MI5.
A Hungarian professor and his wife come to stay at Netherwood. They are Soviet agents hunting the 'Z' File as Stalin believes it proves collusion between British Intelligence, Churchill, and Hess. Will is the victim of a honeytrap and agrees to fetch it. He discloses the plot to 'M'. At the handover on the coast, commandos ambush and kill the Hungarian couple. In disgust, Will renounces the idea of becoming a priest.
Crowley dies at Netherwood on 1 December 1947. Will finds a silk handkerchief under his deathbed inscribed with a map of Dungavel and Hess's alias. Will learns from 'M' that Crowley has sent the 'Z' File to Jack Parsons, an American disciple and rocket scientist. Will visits him and his wife Cameron in Pasadena in 1952. He and Jack perform an Enochian ritual in the desert. Ten days later Parsons blows himself up before he can give Will the file as promised.
In May Knight invites Will to his suburban house. Will goes intending to use th