Set in Eurobis, a continent divided between the Witch Kingdom and rival Vampire Kingdoms, the novel takes place in a world where witches each possess a single type of magic that can be stored in enchanted cards. Voids, humans born without magic, rely on these cards and occupy the lowest rung of witch society.
Samara Koisemi, a twenty-year-old void, has spent twelve years as a servant in Greymere, a prison whose walls suppress all magical abilities. Sentenced at age eight, she survives by catching rats, avoiding notice, and enduring the cruelty of Nelson, a disgraced noble's son who oversees the servants. Samara clings to the hope that after her fifteen-year sentence ends, she can join the Monastery, a religious sanctuary that accepts even criminals.
When a new prisoner arrives and is whipped for hours, Nelson orders Samara to tend the man's wounds. She discovers the prisoner is a vampire with glowing red eyes and a flayed back. A vampire killed Samara's mother when she was a child, and the trauma makes the encounter excruciating. She applies healing salve, and the vampire attempts to use thrall, a vampire's ability to mentally compel humans, to order her to free him. She refuses.
The next day, Nelson reveals he controls when Samara's sentence ends and has no intention of releasing her. That night, she steals his key and offers the vampire a deal: She will unlock his shackles if he gets her out unharmed. He agrees.
The vampire kills Nelson and the guards at the exit. Outside, Samara sees the sky for the first time in over a decade. The vampire argues she will be hunted without his protection and proposes she accompany him to Apante, the City of Answers, where he needs her to enter the Great Library, whose magic compels its Librarians to answer any question but bars vampires from entering. She agrees.
Over days of travel, mostly at night, Samara learns his name is Raphael. She applies salve to his back, which heals slowly because the sun and animal blood weaken his recovery. At a village, she buys enchanted cards, including one to resist thrall. At a tavern, Raphael reveals his thrall does not work on Samara and admits vampires are incapable of lying. When Thomas, a young man who flirted with Samara at the village, reappears at an inn and corners her in a stable, Raphael kills him, declaring Samara is his.
At Apante, Raphael instructs Samara to ask the Librarians how to gain possession of the Black Grimoire, a mythical book of death magic. The Librarian reacts with alarm but is compelled to answer: The grimoire lies in the Temple of Anagenni, the goddess of death, in the northern marshes, guarded by unknown traps.
They part ways, and Samara goes to the Monastery. The head priest, Devoin, orders her to beat herself with a scourge; when her hidden cards fall to the floor, Devoin takes over the beating. Raphael, who has remained nearby, intervenes and kills everyone in the room. He carries Samara to an abandoned cabin and tends her wounds for weeks. With nowhere else to go, she agrees to accompany him to the temple.
Inside the Temple of Anagenni, Samara feels the temple's power resonating within her inexplicably. They find the Black Grimoire on a stone lectern, but Raphael cannot touch it; the enchantment repels vampires. When Samara lifts the book, a trap fires cursed copper arrows from every direction. Raphael shields her with his body, absorbing over a dozen. Gravely wounded and unable to heal without human blood, he faces death. Despite vowing never to let a vampire feed on her, Samara offers her neck. The bite produces intense pleasure rather than pain. Raphael heals completely, and the feeding creates a permanent mental bond: He can now sense her emotions.
They travel to Damerel, the Western Vampire Kingdom's capital. Upon arrival, a vampire noble attacks Samara, drawn by her blood. Raphael tears the noble's hands off and declares Samara "mine" before the court. The noble addresses Raphael as "my king." Samara faints and wakes to learn Raphael is the Vampire King of the West. He proposes a new deal: one thousand gold pieces to translate the grimoire from Old Runyk, an ancient language she studied as a child. She accepts.
Raphael assigns two guardians: Amalthea, his court seer, an oracle witch who fled the Witch Kingdom as a child to escape execution, and Iademos, his vampire general, known as Demos. Amalthea becomes Samara's first true friend and reveals that Raphael has killed every other human he ever drank from to avoid the emotional bond; Samara is the exception. Demos trains Samara in combat with a cursed bronze dagger.
Titus, the Witch King's spymaster, confronts Samara in secret. He knows her identity and urges her to spy for the Crown, threatening exposure. She refuses but cannot reveal the encounter without raising questions about her past. When the ancient vampire librarian attacks her for translating the grimoire, Samara kills him with her dagger and her last enchanted card.
As weeks pass, Samara and Raphael grow closer. He teaches her to shield her emotions from the bond, builds a hidden sleeping compartment in her bed because childhood trauma prevents her from sleeping exposed, and brings musicians to the castle because she once mentioned she loved music. She translates the grimoire's opening passage and discovers the truth: The necromancer is a witch born every two hundred years with the power to control vampires. She withholds this from Raphael.
Samara sneaks into a blood den, where humans sell their blood to vampires, and finds a girl weakened from overfeeding. A drunk vampire attacks Samara; Raphael kills him. They share their first kiss. When she asks if he believes the system is fair, he answers: yes. Days later, Samara and Amalthea find the donor girl dead, her throat torn open. The sight mirrors Samara's mother's death and triggers her childhood trauma. She agrees to cooperate with Titus.
Titus's plan centers on the Tri-Lunar Eclipse Ceremony, a sacred ritual where the king drinks from his Chosen before the court. He gives Samara a poison card made from his own toximancy, a magic of poisons, and a royal pardon. She activates the card. At the ceremony, Demos reveals Raphael has secretly ordered his men to hunt the donor's killer. When Raphael bends to bite Samara, she cries out and refuses. She cannot poison him.
In her chambers, Titus confronts her. He reveals he orchestrated the librarian's attack and the donor girl's murder to manipulate Samara's hatred of vampires. He also confesses to killing her mother. Samara fights him, but Titus uses his toximancy to paralyze and stab her.
Raphael bursts in, sensing Samara's agony through the bond, and kills Titus. Finding Samara dying, he drains her blood and feeds her his own, turning her into a vampire despite having promised never to do so.
Samara wakes in a cell behind cursed copper bars with no heartbeat. Demos reveals Raphael is in a coma from the poison Samara carried in her veins. When Demos pushes a goblet of blood through the bars, Samara hurls it away and instinctively commands him to leave. His eyes glaze over as he obeys, compelled by her voice alone. She realizes she is the necromancer Raphael has been hunting, the witch born with the goddess Anagenni's blessing to control the undead. The novel ends with Samara vowing to tear his kingdom apart.