Elisabeth Scrivener was abandoned at the Great Library of Summershall as a baby and has spent her entire life being raised among its books and grimoires — living books of magical spells. Now 16, she is an apprentice librarian under the tutelage of the library’s wardens and Director. Elisabeth hopes to one day become a warden herself, as she can imagine no other life than that within the walls of one of Austermeer’s six Great Libraries. Five are evenly spaced in a circle with the sixth located in the circle’s center, the capital city of Brassbridge.
One night, Elisabeth wakes and is convinced she heard a sound. She explores the library alone as everyone else is asleep. She recognizes a peculiar odor, *aetherial combustion*. She smelled it the previous year when a young sorcerer, Nathaniel Thorn, had performed a spell in her presence. As a librarian, Elisabeth has been taught to fear sorcerers because they gain their magic by giving years of their lives to a demon in exchange for the demon’s power. Nathaniel surprised her by being both handsome and kind.
As the smell indicates unauthorized magic has been performed among the grimoires, Elisabeth proceeds with caution. She stumbles across the Director’s legendary sword, Demonslayer, and then finds the Director dead. Picking up the sword, Elisabeth realizes one of the grimoires has been turned into a Malefict — a hybrid book-demon, who is able to walk on its own and kill humans. Terrified, she follows its trail, and after a brutal fight, destroys it.
Although she should be hailed as a hero, a vindictive library warden insists Elisabeth is responsible for the Director’s death and the creation of the Malefict. He summons a sorcerer to take her to trial in the capital. Elisabeth is shocked and unnerved when her escorts are none other than Nathaniel Thorn and his man servant, Silas.
When they reach the capital, they are set upon by lesser demons, called fiends. Nathaniel is surprised when Elisabeth refuses to run for safety and instead picks up an iron rod to fend them off, as demons are weakened by iron and salt. Nathaniel uses magic to fight the beasts, but Elisabeth is injured when she lures a demon away from a young boy. Before falling unconscious, she sees Silas remove his livery gloves in order to join the battle and learns he has claws instead of fingers.
Elisabeth awakens in the guestroom of Nathaniel’s family mansion with Silas preparing her a cup of tea. She remembers seeing his claws and realizes he must be the demon to whom Nathaniel is bound. Silas’ demeanor totally betrays all she has been taught. He is kind and attentive to her needs. He assures her that while lesser demons feed on human flesh, he is high born and only consumes the life force of the human with whom he has bargained. He shows her the morning papers, which declares her a hero and calls for all charges against her to be dropped. That evening, Nathaniel escorts her to Chancellor Ashcroft’s house, the judge in her case.
At dinner, Chancellor Ashcroft commends Elisabeth’s actions both in the death of the Malefict and the battle with the fiends. He drops all charges. What should be a joyous night turns bittersweet when Nathaniel and Silas leave her in Ashcroft’s care and return to the Thorne mansion.
Elisabeth is given a beautiful room and dresses in Ashcroft’s home. He parades her out as his special guest at a dinner with Parliament dignitaries and their wives. After dinner, she tries to find her way back to her room but instead comes upon Ashcroft’s demon, Lorelei. The beautiful creature casts a spell that should render Elisabeth helpless both physically and mentally. Elisabeth, however, conceals the fact that her mind remains clear.
Lorelei brings her to Ashcroft’s study where the demon and the Chancellor converse openly, believing Elisabeth to be devoid of thought. Elisabeth learns that the Chancellor murdered her Director and created the Malefict. She realizes he has brought her here as his prisoner to learn if she knows anything about his crime. Lorelei lifts the spell from her, and Ashcroft tells Elisabeth she must have fallen unconscious after dinner.
In the morning, Elisabeth tries to convince a physician of Ashcroft’s guilt, but he believes her to be suffering an inflammation of the brain due to excessive reading. Although distressed by his chauvinism, she is relieved to learn he does not tell Ashcroft about her suspicions.
Over the next few days, Elisabeth realizes many of Ashcroft’s servants are actually lesser demons. Every afternoon, Lorelei places Elisabeth under a glamour so Ashcroft can question her about what she knows about his crime, but she is able to evade the truth. Lorelei encourages him to enter her mind and take the memories by force. Because such an act drives the victim insane, Ashcroft wants to wait.
Ashcroft’s patience ends a few days later, and he enters Elisabeth’s mind, seeking to rob her memories. Elisabeth is still able to keep her knowledge a secret from him. Frustrated, Ashcroft pulls himself from her memories, leaving Elisabeth screaming as he tries to destroy the rest of her mind. He intends to have her committed to a mental institution, but she escapes.
After several days of living on the streets, Elisabeth thinks of Nathaniel and wonders if she might be able to trust him. Almost immediately she sees Silas across the street. When she tries to catch up to him, she is accosted by men in an alley. Silas rescues her and takes her back to Thorne mansion.
The following day, Elisabeth tells Nathaniel the truth about what happened at the Summershall Library and Ashcroft’s part in it. At first, Nathaniel refuses to help Elisabeth in her quest to discredit the Chancellor, afraid that she will be hurt or killed.
Nathaniel finally agrees to help Elisabeth in her search for proof of Ashcroft’s duplicity. When nothing turns up, they decide to confront Ashcroft at the upcoming Royal Ball. They can’t make an official accusation, but they can denounce him before his peers and hopefully spark others to be wary of him.
While their plan initially succeeds, Ashcroft uses a spell to lure them away from the crowds and into a garden. There, Ashcroft appears with Silas as his prisoner. He offers to trade Silas in exchange for Elisabeth. Instead, Nathaniel challenges him to a dual. In the end, Elisabeth kills Ashcroft’s demon, leaving him without magic. Silas then steps in front Ashcroft’s sword, sacrificing himself for Nathaniel.
Elisabeth takes Nathaniel home to nurse his severe injuries. He enlists her help to summon Silas back from the Otherworld. The demon comes but is no longer under Nathaniel’s command. Elisabeth sees him for the monster he is, and he admits he only gave his life because he knew Nathaniel would summon him again.
Silas demands Nathaniel now give him 30 years of his life or he won’t enter his service. Horrified, Elisabeth offers Silas 10 years of her life if he will only take 20 of Nathaniel’s. The demon agrees, although he will only serve Nathaniel, not Elisabeth. As Nathaniel heals, the relationship between him and Elisabeth becomes a romantic one.
Nathaniel and Elisabeth continue to work together to fight Ashcroft. They soon learn he has been killing people in the Great Libraries as a blood sacrifice. His ancestor placed the libraries in points on a pentagram, serving as a massive demonic summoning circle. Ashcroft has discovered the secret name of the demon king, Archon.
Ashcroft plans to make one last sacrifice in Brassbridge and summon Archon to the world. He believes it will open up a new era of sorcery and change the world. Nathaniel and Elisabeth learn that this summoning will destroy the world, as Archon’s presence will tear the veil between the Otherworld and earth, allowing demons to invade and kill. No one will be able to stop them.
Elisabeth and Nathaniel’s warnings go unheeded, and Ashcroft succeeds in creating an initial rift between the worlds. Demons flood in and begin to destroy and kill all who get in their way. Elisabeth and Nathaniel find Ashcroft in the Royal Library still in the act of calling Archon to the world.
By growing up with the books, Elisabeth has learned that she has a magical connection to them. She rallies them to fight the demons. But even with their help, it is soon evident that Archon is too powerful to be contained. Nathaniel is mortally wounded, and Elisabeth expects to be killed. They free Silas from their bargain.
The demon servant transforms into his Otherworld form: glowing, horned and evil. Even as Silas prepares to kill them, Nathaniel takes his clawed hand and forgives him. Stunned, Silas goes against his nature and fights Archon. The demon king is too strong to defeat, but Silas ends the ritual and banishes Archon back to the Otherworld, even though it means his own eventual death.
In the following weeks, Elisabeth is given the opportunity to return to one of the libraries as an apprentice, but she is unsure of what she wants for her future. She only knows she wants it to involve Nathaniel. Although the two tried many times to summon Silas from the Otherworld using his true demon name, they were unsuccessful.
Elisabeth mourns the loss of the demon, and one afternoon in an act more of memorial than summoning, she lights the candles around the pentagram one more time and places a few drops of her blood onto the circle. Then, instead of using his true name, she calls for Silas. A breeze stirs in the room and blows out the candles.