Sheila Masterson’s 2025 novel, The Poison Daughter, is a standalone entry in the popular dark romantasy subgenre, which blends high fantasy with dark romance. Set in the walled city of Lunameade, the story follows Harlow Carrenwell, the youngest daughter of the city’s magical ruling family. Cursed with a poison kiss that kills instantly, Harlow secretly operates as the “Poison Vixen,” a vigilante who targets abusive men. Her mission is upended when she is forced into an arranged marriage with Henry Havenwood, the mysterious heir of a rival fort, who proves to be the one man immune to her deadly touch.

The Poison Daughter is Masterson’s seventh novel and continues her work in the fantasy genre, which also includes The Lost God and Fable Song series. The narrative explores themes such as Feminine Rage as a Response to Systemic Male Violence, Revenge as a Self-Destructive Pursuit, and Breaking Family Cycles of Abuse. The book became a popular success, particularly on social media platforms like TikTok, where the romantasy genre has flourished.

This guide refers to the 2025 Sheila Masterson e-book edition.

Content Warning: The source material and guide feature depictions of graphic violence, physical abuse, emotional abuse, child abuse, child death, sexual content, sexual violence, rape, mental illness, suicidal ideation, illness, and death.

Plot Summary

In the walled city of Lunameade, protected from vampiric creatures called the Drained, Harlow Carrenwell lives a double life. As the youngest daughter of the city’s ruling family, she possesses a poison kiss, a blessing from the Divine of Fortune, Harvain, that kills anyone she kisses. While her family, the only magic-wielders who can see the colorful auras of Divine blessings, uses her as a political assassin, Harlow secretly operates as the “Poison Vixen,” a vigilante who kills abusive men. Her mission is fueled by the abuse her beloved sister, Aidia, endures from her husband, Rafe Mattingly, the city’s mayor. Harlow is reunited with a bruised Aidia at a family dinner, where she vows to secretly kill Rafe. However, her plans are disturbed when her father, Harrick Carrenwell, announces that Mountain Haven, a neighboring fort thought to be destroyed by the Drained 10 years prior, has reestablished contact. To solidify an alliance, Harrick declares he has betrothed his youngest daughter, Harlow, to the heir of the mountain hold. As a widow whose first husband was a political target whom she slowly poisoned, Harlow is furious at being trapped into another fake marriage, though she hides her feelings, as per the Carrenwell creed.

Determined to complete one last job as the Poison Vixen, Harlow meets a client who claims that her husband, Ron, is abusive toward her. The client describes him as a charming man with dark hair who wears a navy coat with gold embroidery and gives women a white rose. That night, Harlow, using a glamour from a magical star-shaped pendant to alter her appearance, finds her mark, who calls himself Asher, at the Heartless Haven Pub. He is immune to her poisonous kiss; instead of dying, he becomes intensely aroused, and their encounter becomes a passionate make-out session before Harlow, confused and unnerved, flees. The next day, she formally meets her betrothed, Henry Havenwood, who is revealed to be Asher. Henry does not expose her assassination attempt, instead choosing to blackmail her into getting to know him. In the Carrenwell garden, they have a tense confrontation where he reveals he wore a ring that hid his magical aura, which is why she couldn’t identify him. At their engagement party, a bomb detonates, an attack by rebels led by a mysterious figure named Rochelli. Henry shields Harlow from the blast and uses his healing magic, a gift from the Divine Elvodeen, to save her injured brother, Kellan, captain of the city watch. In the chaos, Rafe confronts Harlow, revealing he knows the secret of her poison kiss. Henry’s father announces that they will immediately leave for Mountain Haven given the danger in Lunameade. Harlow is to accompany them with her bodyguard, Gaven, for the upcoming wedding.

The journey to Mountain Haven is perilous. Their party is attacked by a horde of Drained in a supernatural blood mist. Harlow discovers she can see the creatures’ “aura voids” (a negative space symbolizing a lack of life), allowing her to anticipate their movements, while Henry reveals that water from the Havenwood’s private well can be used as a weapon against them. After being wounded, Harlow suffers a debilitating pain episode, a chronic condition she hides from everyone. Henry tends to her, and during her recovery, she learns from her parents that her brother Able is descending into “madness,” which they suspect is caused by overuse of their family’s private well. The new couple’s fragile truce builds as they share secrets: Henry reveals he is a “Deathless” being, resurrected by his mother, Evangeline, after dying in the attack 10 years ago. A gift from the Divine Asher ensures he cannot be killed the same way twice, which explains his immunity to her poison. Harlow, in turn, reveals the truth about her pain episodes and shows Henry the star-patterned brand on her back, confessing it was created by Aidia to cover scars from their father’s abuse. All Harlow now wants is to help Aidia escape Rafe. Henry promises to help.

Their bonding is shattered when Henry discovers Harlow sneaking into a restricted “hunt,” a ritualistic orgy to the Divine of Pleasure, Kennymyra. He claims her by having sex with her and biting her neck and drinking her blood, a consensual act that binds her to him and reveals his full Deathless nature.

News of an attack on Lunameade draws Henry and Harlow to the city. At Lunameade, Kellan shares a secret with Henry. Aidia, the sister whom Harlow wants to save, died six months ago. Henry interprets the tale as Harlow attempting to manipulate him with a fake story and forces her to look at Aidia’s tomb. Harlow’s memories return in a rush, revealing the horrifying truth that she herself killed Aidia under the manipulation of Rafe. Henry realizes that Harlow was not lying about Aidia to con him; her trauma genuinely made her believe her sister was still alive. Henry also learns that Harrick and Liza have a huge role to play in the death of Aidia.

That night, Harlow confronts her parents at a private dinner. She poisons their soup with Stellarium Blossoms, a paralytic, and Polm’s Opus, an influence agent, rendering them helpless. With Kellan using his own manipulation magic to compel them, Harlow forces her parents to confess their greatest secret: They allowed Rafe to use his magic to compel Harlow to push Aidia from a balcony, causing her death six months prior. For six months, Harlow’s grief-stricken mind had blocked the memory, creating visions of a living Aidia. In a storm of vengeful fury, she makes her parents torture each other before killing them both with a poison called Asher’s Anthem.

Harlow confesses her murder of her parents to Henry, and he accepts the news without judgement. The two make love, both realizing they have fallen in love with each other. However, next morning, Harlow senses from Henry’s aura that he is twice-blessed, possessing a hidden gift from Polm, the Divine of Malice, which allows him to manipulate emotions. Henry confesses that he manipulated Harlow’s feelings at the start of their relationship. Feeling betrayed, she runs from him. On the final day of the Dark Star Festival, a city-wide celebration, Kellan reveals himself to be the rebel leader, Rochelli. He publicly exposes his parents’ crimes: They murdered any child blessed with holy fire to maintain their power monopoly and deliberately redirected the Drained horde toward Mountain Haven 10 years ago to consolidate their control over a fearful populace.

Kellan takes public responsibility for his parents’ deaths and begins reforming Lunameade, ending the oppressive blood tithes. Henry, with the help of his friends Carter and Bryce, captures Rafe. He tortures Rafe, recreating the injuries he inflicted on Aidia, before compelling him to jump to his death from the same manor balcony. Harlow, reeling from the truth and revelation about Henry, retreats to an apartment across from Guardian’s Crossing, a bar run by her friend and former lover, Beatrice “Bea” Grange. There, she has a final, cathartic internal conversation with the memory of Aidia, who encourages her to let go of her grief and accept Henry’s love. After revealing her parents’ madness was caused by the well being poisoned by the citizens’ resentful blood tithes, Harlow gives Kellan the information from Mountain Haven about using well water against the Drained. The next morning, as the city celebrates a new dawn, Henry finds Harlow in the central square. He confesses that since their confrontation, he can see color for the first time in 10 years, a sign among the Deathless that he has found his true love. He apologizes for his deception and asks her to return to Mountain Haven with him. Overwhelmed but no longer running from her feelings, Harlow challenges him to a race, their shared laughter signaling the start of a new, honest chapter together.