Lucas Corso is a middle-aged book dealer with a reputation of doing anything—regardless of legality—for his privileged clientele. While in
Madrid attempting to authenticate a previously unknown partial draft of
The Three Musketeers, he is summoned to
Toledo by Varo Borja, a notoriously eccentric and wealthy collector. Borja has obtained a copy of a legendary book,
Of the Nine Doors of the Kingdom of Shadows, whose author was burned at the stake by the
Inquisition. The book purportedly contains instructions for summoning
the Devil. Only one copy of the book is supposed to have survived, but Borja claims three exist, two of which are elaborate forgeries. He hires Corso to compare the three copies and obtain the legitimate one by any means necessary. He promises to pay handsomely and cover all expenses. Corso agrees, but continues to research the partial
Dumas draft. The widow of the draft's previous owner, Liana Taillefer, insists the draft is a fake, but offers to buy it from Corso. After several encounters, she attempts to seduce Corso to obtain the draft; when he succumbs to her charms but refuses to surrender the manuscript, she becomes his enemy. She imagines herself as
Milady de Winter, and uses a male associate (whom Corso nicknames "
Rochefort") to follow Corso and attempt to retrieve the manuscript by force. Corso confers with the Ceniza Brothers, book restoration experts with extensive knowledge of forgery. They give him basic knowledge to help him compare the copies of
The Nine Doors. On his way to
Lisbon to visit the owner of one of the copies, he encounters a beautiful blonde with striking green eyes. She identifies herself as
Irene Adler, and suggests that she is a
fallen angel. They part company before he meets with Victor Fargas. Fargas is a renowned collector who has been selling off his extensive library to maintain his ancestral mansion. Corso compares Fargas' copy of
The Nine Doors to Borja's, and finds subtle differences in the illustration plates. Most bear the initials of the book's notorious author, but some of the plates bear the initials "L.F." As Corso returns to his hotel, Irene guards Corso against an attack by Rochefort. Corso leaves her to arrange a robbery of Fargas' mansion to obtain his copy of the book. Irene informs him that Fargas has been murdered and his copy has been burned. She and Corso leave for
Paris. Corso confers with Replinger, an antiquarian and Dumas scholar, who authenticates the Dumas manuscript. As they talk, Corso spies Liana. He returns to his hotel and bribes the concierge to locate her hotel. Irene visits him, and they discuss theology; she implies that she is a witness to the events of the
War in Heaven. Corso visits Baroness Ungern, whose charitable institution possesses the largest occult collection in Europe, including the third copy of
The Nine Doors. They discuss the book's author, before Corso blackmails her with photo evidence of her Nazi sympathies so she will let him examine her copy. Irene calls to warn Corso that "Rochefort" is waiting outside. The Baroness translates the illustration captions while Corso compares Ungern's copy to Borja's. Later, Corso realizes that, while none of the three sets match each other, the plates bearing the initials L.F. form a complete set of nine without duplications, and realizes the nine illustrations form a list of instructions for the famed summoning ritual. Rochefort attacks again, and is again repelled by Irene. Using the concierge's information, Corso confronts Liana and her associate, but Rochefort renders him unconscious. When he revives, Borja's copy and the Dumas manuscript are gone. He learns that the Baroness has been killed in a fire at her library. Using Liana's obsession with Milady de Winter, he traces her to
Meung, where he is captured by Rochefort. Rochefort is instructed by a man calling himself
Richelieu to bring Corso to a nearby castle. Richelieu introduces him to the Club Dumas, a literary society of wealthy Dumas enthusiasts, who are gathered for their annual banquet. Corso is astonished to find that they only want to see the Dumas manuscript, and know nothing about
The Nine Doors. He is invited to stay for the party, but chooses to leave. Corso returns to Spain to confront Borja. Irene insists that she is a fallen angel who has wandered the earth for millennia searching for him. Corso does not question this, and finds himself even more strongly attracted to her. He accuses Borja of being responsible for both murders. Borja, intending to use the ritual described by the book's true nine plates to summon
the Devil and gain ultimate knowledge, has destroyed his entire library to prevent others from following his lead. Corso demands payment, but Borja ignores him and begins the ritual. Corso leaves in disgust; as he leaves, he hears Borja's screams of anguish as the ritual goes awry, remembering the Ceniza Brothers' discourse on false books and realizing one of the plates is a forgery. He joins Irene outside, and surmises that each of them will get the devil they deserve. ==Literary references==