The following version of this book was used to create the guide: Legrand, Claire. Sawkill Girls. Katherine Tegen Books: An Imprint of HarperCollins Publishers, 2018.

Sawkill Girls by Claire Legrand began with the description of Sawkill Rock—its ocean view, horse pastures, and wealthy, beautiful people. Marion Althouse, her mother, and her sister, Charlotte, were rebuilding their lives after her father's tragic death by moving to Sawkill Rock. They would be the housekeepers for the Mortimer women in the Kingshead mansion while living in the cottage next door. Once they arrived, Ed Harlow, the police chief, insisted Marion mount his horse, Nightingale. Once she did, Nightingale ran at full speed. Zoey Harlow, snooping in her father's office for information on her missing best friend, heard the commotion and followed Nightingale on her bike. Marion was thrown from Nightingale in a clearing, regaining consciousness with a scream. Val Mortimer, compelled by her demonic master, followed Charlotte to the scene. Zoey confided in Grayson that she believed Val and her family were involved in the generations of girls' mysterious disappearances on the island. When Marion regained consciousness once again in the cottage, she experienced a foreign heat and pain in her head. The Rock accepted that "the girl" must endure the pain to help create "an infantry" (55).

Val met the Collector in "the circle of stones" in the Kingshead Woods as per their agreement (59). The demon could take many forms now that he gained strength, but was still physically anchored to Val and her mother. Meanwhile, Zoey found a strange, hidden book belonging to her father with depictions of creatures with "colorless white eyes" and Latin inscriptions (66). A week after her accident, Marion continued to experience severe head pain. At Val's party, Zoey was unsuccessful in keeping Charlotte away from Val. In the cottage, "the bone cry" raged inside Marion's head, and she followed the direction of the cry (95). She met Zoey outside, who followed her into the woods, both stumbling upon unfamiliar stones. Marion awoke the next morning to her room full of moths and devoid of Charlotte. The Rock knew that the beast had struck again.

Val, struggling with Charlotte's death, allowed herself to be comforted by the demon who controlled her and generations of women before her. When Zoey returned to the site of the stones, the terrain was no longer the same. An unfamiliar version of Marion spoke to her before being scared away. Meanwhile, Marion followed the bone cry to Val's room in Kingshead and then, when Zoey and Grayson arrived, the forbidden library. Inside, the bone cry led her to books that unhinged the bookcase from the wall. The three descended the hidden staircase to find a basement with an eerie bedroom attached. That night, Val attempted to comfort Marion. A few days later, Zoey heard Marion and Grayson talking to peers about the Collector's local lore. Marion's bone cry erupted when Val approached, and Zoey felt a surge of electricity through her that, through her palm, sent Val flying backward. Marion insisted to Zoey that she could retrieve information from Val if she seduced her. Meanwhile, Zoey found her father's secret basement. After another kill, Val continued to feel guilty. Marion approached her in the stable, where they shared a secret kiss.

That night, Marion watched as a horse broke through its fence, and the bone cry insisted that she follow. She teleported across the island, and then to a strange, snowy beach in another world. When Zoey's father confronted her once again about his book, a moth told her to run. She realized that her father's basement was dedicated to studying the missing girls. After her second horse encounter, Marion recovered with a moth until she teleported to the kitchen in time to see "the not-Marion," with eyes "round and white," turn and run into the woods (242). Marion confided in Zoey, who confirmed that Marion "tessered," like her father's book said (247). They both watched a secret video from her father pleading with Zoey to leave the island. Her father and FBI Agent Briggs explained their involvement with the Hand of Light, an "ancient organization" dedicated to ridding the earth of demons of the "obscura" from the world (248, 254). Val visited Marion, and despite Zoey's suspicions, Marion and Val shared a physically intimate moment.

As Val endured her mother's punishment for leaving behind Charlotte's severed hand, Val's body grew hot and bright, and her hand scorched her mother's skin. The Collector was hungry again, and although Val attempted to save her friend, she was unsuccessful. He sensed Val's intense feelings for Marion and pursued that, attacking Zoey and Marion in the cottage. Zoey flung him away just before Marion tessered them to Zoey's house. Seeing more depictions of "extraordinary girls" in the book prompted Zoey to want more help, but the Rock physically kept her from leaving the island (310). Val found her mother's battered corpse in the red room, and the Collector forced her to become his new queen.

Grayson's research revealed that the Hand of Light expected the girls to sacrifice themselves in order to banish the Collector. In a failed attempt to clear Val's name, Marion discovered Val’s mark of the queen. All three were lured to the cottage, where the Hand of Light trapped them. Zoey's rage began a battle, but Marion, perceiving the Collector nearby, tessered the three of them to a smaller island off of Sawkill. There, Val was possessed by the Collector, gaining moments of consciousness as Zoey and Marion helped her hands burn out his connection to her.

The Hand of Light pursued them with weapons back to Sawkill, and they seized the girls in the woods. Marion called upon the Rock, which sent horses stampeding over the Hand of Light. Freed, the girls found the Collector in the stones. They assumed their positions, and Marion tessered them all to an unfamiliar "salt flat" (409). There, the Collector reformed as a giant monster, swatting away Val and Zoey's attacks. Marion pulled the demon with her through her portal to the Far Place while sending Val and Zoey to Sawkill. Back at home, Val was determined to find Marion. She and Zoey ventured to the lighthouse for weeks, using Val's light as a beacon to guide her home. In the Far Place, Marion slowly formed back into a girl and followed Val’s light through the ocean to return once and for all.