A Killing Cold

A Killing Cold (2025) is a domestic thriller by Kate Alice Marshall. Marshall is the author of multiple best-selling novels, including What Lies in the Woods and the young adult novels I Am Still Alive and Rules for Vanishing. A Killing Cold follows Theodora “Theo” Scott as she accompanies her fiancé, Connor Dalton, to his wealthy family’s isolated mountain retreat for the holidays. Once there, Theo begins experiencing fragments of recovered memories that suggest a connection to the family’s dark past. As Theo uncovers long-buried secrets, she must confront the dangerous lengths to which the Daltons will go to protect their reputation and fortune. The novel explores The Reclamation of Identity Through Memory, Wealth as a Means to Suppress the Truth, and The Thin Line Between Loyalty and Complicity.

This guide refers to the 2025 Flatiron Books edition.

Content Warning: The source material and guide feature depictions of illness, death, death by suicide, graphic violence, child abuse, physical abuse, pregnancy loss, sexual content, substance use, and cursing.

Plot Summary

In the Prologue, a young girl and her mother are in an isolated house in the woods, seeking safety from an unnamed “monster.” The mother reassures the girl, but dread and the anticipation of the monster’s arrival permeate the scene. When the monster arrives, the moment establishes a pattern of hiding and trauma that will echo throughout the protagonist’s later nightmares.

In the present day, Theodora “Theo” Scott travels with her fiancé, Connor Dalton, to Idlewood, the secluded mountain retreat owned by the Dalton family. Connor prepares Theo for her first meeting with his wealthy family. During the drive, they nearly hit an injured deer. When Theo approaches the fallen animal, it suddenly rises and flees, causing her to fall. Daniel Vance, the family’s groundskeeper, appears and asks if Theo has ever been to Idlewood before. Theo is already on edge from receiving anonymous texts warning her to stay away from Connor. She keeps these threats private, increasingly certain that her past is catching up with her.

At Idlewood, Theo meets Connor’s older sister, Alexis Dalton; Alexis’s wife, Paloma; and their young son, Sebastian. Alexis is initially skeptical but promises to help Theo navigate family dynamics. Connor’s father, Liam Dalton, died young under tragic circumstances, leaving his children affected by his death. Connor and Theo settle into the White Pine cabin, set apart for privacy and always assigned to the newest couple. Theo reflects on her fragmented childhood memories, her lack of knowledge about her real name or origins, and her troubled upbringing with her adoptive parents, Beth and Joseph Scott. Alone in the cabin, Theo checks Connor’s phone for evidence about the threatening messages but finds nothing conclusive.

That evening, Theo meets the entire Dalton family at dinner: matriarch Louise Dalton, patriarch Magnus Dalton, and uncle Nick Dalton. Louise interrogates Theo about her education and family history. Theo claims that she is an orphan, giving evasive or false answers to please the family. Conversation grows tense, especially regarding the abandoned fifth cabin, which the family claims is in disrepair. While speaking privately with Theo after dinner, Alexis expresses a grudging, conditional liking for Theo but warns her not to hurt Connor.

Theo suffers recurring nightmares filled with symbolic images: an antlered man, a buzzing dragonfly, and a red star. At night, she discovers footprints outside the cabin leading to their bedroom window. Her investigation leads her to the neglected fifth cabin, which she has the strong but seemingly impossible sense that she has been before. Vance warns her about the dangers of the woods and confirms that the cabin hasn’t been used since Liam’s death at Idlewood, leading Theo to initially assume that Liam died at that specific cabin.

In the following days, Theo participates in the family’s traditional “Pie Day” baking with the Dalton women, including newly arrived Rose Dalton—Liam’s widow and the mother of Connor, Alexis, and their brother Trevor. Rose scrutinizes Theo’s dragonfly tattoo. Theo calls it a “personal symbol,” though Rose seems unconvinced and disdainful. Magnus invites her to help dress a deer, testing her resilience. He questions her about her family and bloodline, emphasizing his belief in family legacy and strength. Later, Theo overhears Louise, Rose, and Alexis discussing what Connor might have revealed to her, hinting at hidden family secrets.

The sense of threat intensifies. Theo discovers a gift-wrapped box labeled “DORA,” her childhood nickname, on her windowsill. The box contains a note: “You shouldn’t have come” (60). Realizing that the threats come from someone at Idlewood, not from her past life elsewhere, Theo becomes increasingly fearful but hides it from Connor. The dragonfly motif persists in her nightmares and on her tattoo, suggesting ties between her identity and Idlewood.

During a cross-country skiing trip with the family, Rose questions Theo about her plans with Connor and suggests that Theo should insist on a prenuptial agreement to protect herself as well as the wealthy family. Later, driven by intense curiosity, Theo enters the abandoned cabin and discovers a brass dragonfly ornament matching her tattoo. She finds a photograph of herself as a young child with Liam, confirming that she lived at Idlewood as a child. Internally conflicted, Theo struggles with whether to reveal this to Connor.

While looking after Sebastian, Theo encounters Nick, whose questions about her childhood nickname, Teddy, seem suspicious. Later, while searching for Sebastian’s book in Alexis’s suitcase, Theo discovers hidden photographs of a battered young woman. The identity of this woman and the source of her injuries are initially unknown to Theo but hint at deeper Dalton family secrets.

The next day, Nick tells Theo that Liam had a mistress, Mallory, and a daughter, Teddy, living in the fifth cabin at the time of his death. He claims that the woman and child disappeared following Liam’s accident and that the family shielded Alexis and Connor from the details.

The family dinner that night is disrupted by mysterious ornaments appearing on the Christmas tree, each containing evidence of infidelities, accidents, and family secrets. Trevor confesses to orchestrating the incident to expose family secrets. One photograph implicates Alexis in marital infidelity, leading to conflict between Alexis and Paloma. Amid the chaos, Theo realizes the family’s willingness to do anything to protect their reputation.

While investing the abandoned cabin, called “Dragonfly,” Theo runs into Vance, and he gives her a bag containing Mallory’s belongings: her scarf, a teddy bear, and a photograph. He also reveals that Mallory’s daughter’s name was Rowan and that her mother called her Teddy. This triggers more of Theo’s fractured memories and aids her in continuing to piece together her past.

Magnus organizes a hunting trip, separating Theo from Connor. While she waits in the spot where Magnus has told her to wait, Connor, hunting with Nick, accidentally shoots an arrow that slashes Theo’s arm. She initially fears that it was an attempt at murder, but Connor insists that it was an accident. Nick provides first aid, and Vance arrives, heightening Theo’s suspicion that the family is orchestrating attacks against her. (Later, it is revealed that Magnus orchestrated a plan to have Vance kill her during the hunting trip, intending to blame a poacher, a plan that was either preempted or complicated by Connor’s accidental shot.)

Later that night, Theo goes outside to test Magnus’s phone number and discovers that he’s the one who’s been sending her threatening messages. Then, she receives a call from her adoptive father, Joseph, who reveals that he was contacted by a Dalton-hired investigator about Theo’s past. Joseph admits that he sent photographs documenting Theo’s childhood injuries and reveals that her adoption was handled unofficially with money changing hands. He recounts that young Theo used to repeat the word “Teddy” and shared a story about a princess in a castle on a mountain who died, a memory that aligns with Theo’s nightmares.

As she heads back to White Pine in the freezing cold, Theo begins to figure out what her memories mean: Nick is the one who hurt Mallory, and Liam was trying to help her and Rowan (Theo) escape from the cabin. She reveals this to Connor and also confronts him about the circumstances of their seemingly random meeting. He admits that he sought her out after seeing her photograph at an art show: Her dragonfly tattoo reminded him of the “Dragonfly” cabin associated with his late father.

The next morning, Olena, the housekeeper Irina’s daughter and Trevor’s lover, is found dead in the snow near the cabins. Her body is clad in a red coat identical to Theo’s, indicating that someone meant to kill Theo but mistook Olena for her. Panic spreads throughout the family. Magnus, Louise, Nick, and Vance attempt to control the narrative and isolate Theo. Connor and Theo announce plans to leave, but heavy snow makes the roads impassable. Rose brings tea to Theo, not knowing that Louise has drugged the beverage. Rose tells Theo that Connor and Magnus have gone into town, but Theo does not believe that Connor would leave her alone. Fearing for Connor’s safety, she goes to a shed seeking the keys to an all-terrain vehicle so that she can go looking for Connor. Nick confronts her in the shed, and the drug that Rose delivered earlier begins to take full effect. Nick ties up and gags Theo and then moves her to the Dragonfly cabin to facilitate her murder under Magnus’s orders. Vance guards her, conflicted but obedient. He reveals that he was the one who found Theo alive in the snow after Mallory’s death and secretly arranged for Magnus to send her away.

Theo frees herself using Magnus’s hunting knife, helped by Duchess the dog’s intervention. She escapes Dragonfly, hides in the Red Fox cabin with Alexis and Paloma, and urges them to seek out Connor. When Connor appears, Theo and Connor attempt to escape on a UTV. Nick catches up and shoots at them, injuring Connor in the arm. During the ensuing struggle, Theo kills Nick in self-defense.

They return to the lodge, where the surviving family is gathered. Theo and Connor confront the group. Theo reveals her true identity as Rowan Cahill and exposes the violence and cover-up perpetrated by the Daltons. Nick kept Mallory and the young Rowan in a state of near captivity, subjecting Mallory to violent abuse. Liam tried to help her escape, leading to a misunderstanding in which Rose came to believe that Liam, her husband, was having an affair with Mallory. Alexis confesses that, as a distraught teenager, she brought a rifle to the cabin to confront Mallory, hoping to scare her away and restore her family’s happiness. In a heated moment, she accidentally shot Mallory. At the same time, unbeknownst to Alexis, Liam was fighting with Nick, trying to protect the young Rowan. Nick struck Liam in the head with his rifle butt. Liam got away and tried to help Rowan escape, but he soon collapsed and died from the head trauma. Magnus arrived and, seeing Mallory alive and preparing to call for help, stabbed her to “control the situation” and protect Alexis from exposure (283). Louise tries to manipulate the narrative, proposing to frame Theo for Olena’s murder and protect Alexis and the family’s reputation. She admits to drugging Theo’s tea

In a private conversation with Theo, Magnus confesses that he is terminally ill and makes a proposal: stay silent and accept the Dalton family’s protection or expose them and receive little justice due to his terminal illness and vast resources. He offers to reveal the location of Mallory’s unmarked grave if Theo accepts his terms.

When the police arrive, Magnus’s influence ensures that Theo is initially framed and arrested for Olena’s murder. However, Alexis, supported by Paloma and Trevor, eventually gives statements revealing the family’s crimes and the decades-old cover-up. Magnus, dying of cancer, evades prosecution. Louise claims ignorance. Alexis, a minor at the time and deemed not fully culpable, escapes a prison sentence. Alexis and Paloma are separated for a time but remain in contact. Vance vanishes, leaving Duchess with Theo and Connor.

In the aftermath, Theo and Connor marry quietly. Both take the surname Cahill. They adopt Duchess and begin a life together, financially diminished but free from the Dalton legacy. Theo chooses to keep the name Theo Rowan Cahill, combining her chosen name with her birth name. She never learns her mother’s grave location, as Magnus dies without disclosing it. In the closing scenes, Theo imagines wildflowers blooming over Mallory’s resting place. With Connor and Duchess, she watches the sunrise and reflects on her reclaimed identity, closure, and survival, at last able to choose her own future.