August Winthrop, an American who fought with the International Brigade in 1937, is talked into returning a 17th century chronicle containing a great mystical secret written by a Spanish Jewish physic fleeing both the Inquisition and the witch trial of Logrono. It means August will have to risk his life and possible arrest to return the book to the Basque family who have been safeguarding it for centuries. Meanwhile, unknown to August, three other parties seek both the chronicle and August -- a maverick CIA operative who has killed in the past in his desperate search for the chronicle and will kill again, a mysterious middle-aged woman who is the secret leader of a band of occultists in thrall to Aleister Crowley, and the MI5 who have become convinced August is a Soviet agent out to sabotage a military pact between Spain and the US.