Back in the present, Marin searches Daisy’s diary for clues after Julianne’s disappearance. Grieving for Julianne, Heather, and Susie, Marin circles the island and finds no trace of them. She’s disturbed by how quickly Julianne’s dress appeared in the oak tree after she vanished. Marin speculates that Azra takes the women and leaves their clothes as an offering, mirroring the ancient practice of placing clothes on the shore to appease witches who allegedly lived on the island. She examines the lightning-scarred oak, recalling the diary’s mention of a “crevasse,” but finds only healed bark.

Overwhelmed, Marin returns to the parlor of the main house to continue her research. Ronan finds her, and they share a brief, comforting moment holding hands until Violet interrupts. Marin explains her theory that Azra is following a pattern. Ronan confesses that, contrary to his earlier claims, he has been smelling the perfume of his deceased girlfriend, Elise, at night. Violet proposes a plan: Since Azra seems to be using their past traumas against them, they should confront those traumas directly by holding another séance.

In another 1926 diary entry, Daisy writes that she’s too afraid to sleep and has moved into the main house with Ruth. Overcome with guilt, Daisy confesses to Ruth that she believes she’s responsible for the disappearances, having unintentionally freed the Darkness during the first séance. 

Ruth suggests that they conduct another séance to ask the Darkness for answers. Though terrified, Daisy reluctantly agrees to hold it the following night, ending her entry with a prayer for her own survival.

Marin, Ronan, and Violet agree to hold the séance the following night, with Marin siding with a hesitant Ronan against an eager Violet. Later, unable to sleep, Marin encounters Ronan in the hallway wearing only his boxer shorts. He initially mistakes her for Elise. Stating that he doesn’t want to be alone, Ronan suggests that they sleep in his bed together. He then kisses Marin without her consent, his hand sliding to the base of her spine. Feeling violated, Marin pushes him away and retreats to her room, apologizing out of shame and confusion.

Distraught, Marin decides to talk to Violet. She finds Violet’s room empty and discovers several books on demonology and witchcraft. At the bottom of Violet’s open suitcase, Marin finds an old, non-functional cell phone, realizing that Violet has kept its existence a secret from everyone.

In her 1926 diary, Daisy writes that she has changed her mind about the séance. Ruth attempts to reassure her, suggesting that the name Azra can mean “light” and that the entity may be trying to guide her toward it. As they prepare, Daisy becomes suspicious of Ruth’s persistent calm in the face of the disappearances. She begins to wonder if Ruth has known what was happening all along. As Ruth summons her to the parlor, Daisy concludes that she’s no longer trustworthy.

Back in the present, Violet returns and confronts Marin about the cell phone. Violet claims that the phone is broken and that she had forgotten about it. Nevertheless, Marin accuses her of intentionally stranding them on the island. 

Marin deduces that Violet and Loretta orchestrated the entire situation, starting by giving Brad un-boiled lake water to make him sick and force Loretta to leave with him. Marin believes that their goal is to replicate the events of 1926. When Marin mentions the other missing actresses, Violet makes a slip, suggesting that they may not be truly gone. When pressed for the truth, Violet gives Marin a coy smile and refuses to comment.

In what she fears may be her last diary entry, Daisy describes the terrifying séance. The Darkness appears behind Ruth, taking the form of Daisy’s abusive father. Daisy accuses Ruth of being Azra, but Ruth clarifies that they’re merely “acquainted” and that she brought Daisy to the island to be exposed to Azra’s “light.” Ruth confirms that the other women are dead and tells Daisy that she was spared because she’s “too powerful.” The Darkness then transforms into a horrifying new face, and as shadows fill the room, Daisy uses her strength to overturn the table and flee to her cottage.

Back in the present, Marin is certain Violet that is behind the disappearances and that she’s Violet’s next target. When she hears scratching at her window, she assumes that it’s the ghost of Molly. This time, Marin grabs a flashlight and shines it on the figure, revealing it to be Susie, who’s soaking wet. 

Susie flees, and Marin gives chase into a misty meadow. Heather and Julianne emerge from the fog and restrain Marin. Violet then appears and, over Susie’s protests, decides that it’s time for Marin to know the truth.

In the next 1926 diary entry, Daisy hears the Darkness follow her, first scratching and then tapping at the window. She sees that rather than the Darkness, it’s actually Ruth trying to get her to come to the “light.” Ruth then breaks down the door. Behind her, the Darkness rises up, and the diary entry cuts off abruptly.

Violet reveals to Marin that the entire haunting was a hoax orchestrated by herself, Loretta, Brad, and the other actresses. She explains their methods: Brad faked his illness, they used extra sets of clothes for the oak tree, Heather hid in a camouflage sleeping bag, and the secret cove was used to get people off the island undetected. The séance effects were achieved with hidden lifts, Susie staging a video, Julianne performing the whispered séance voice, and coordinated movements at the glass. They learned about Marin’s sister through a simple Google search and then used that knowledge to exploit her trauma.

The real motive, they explain, is revenge on Ronan. They were all close friends with Elise, an actress who died by suicide after Ronan seduced her, secretly filmed them having sex, and shared the video with others. Ronan then ended the relationship, after which Elise was fired from the movie (allegedly for lacking experience) and replaced by a megastar. The elaborate ruse on New Avalon was designed to harm Ronan psychologically and force him to confess his role in Elise’s death.

Violet asks for Marin’s help in the final séance to secure Ronan’s confession. Marin is furious, feeling completely used and betrayed by the group’s exploitation of her sister’s death. Unwilling to commit, she walks away. 

Back in her cottage, Marin’s anger boils over. She realizes that she was cast by Ronan as a potential conquest and by Loretta as a gullible pawn. Enraged, she repeatedly kicks the baseboard where Daisy had carved her eponymous wheel a century ago, splintering the wood. When she rips the broken baseboard away from the wall, she discovers several folded, yellowed pages hidden inside: the missing conclusion to Daisy’s diary.

The recovered diary pages reveal the horrific truth of 1926. The terrifying face that Daisy saw in the Darkness was her own. In the cottage, Ruth reveals that Daisy’s nightmares were actually repressed memories of her actions while in a dissociative state. With dawning horror, Daisy realizes that she herself killed the other women. Ruth then surfaces Daisy’s repressed memories of her father’s abuse, and Daisy recalls that she had also killed her father. 

Panicked and in denial, Daisy grabs a nearby knife and fatally stabs Ruth. Overcome with guilt, Daisy buries Ruth, hangs one of her dresses in the oak tree as a memorial, and then adds her own. The diary ends with Daisy declaring that she will die by suicide.

Back in the present, Marin shares the missing diary pages with Ronan and Violet. They learn that Daisy, who was experiencing a dissociative disorder and extreme trauma, was responsible for all the deaths on New Avalon in 1926. The revelation undermines Violet’s supernatural revenge plot. Ronan’s screenplay had ended with Ruth possessed by the Darkness and Daisy killing her by shoving her off the cliff, an ending that Marin considered more plausible than the idea that Daisy was the one who had been possessed. Though the haunting is no longer plausible, Violet insists that an evil entity could still have possessed Daisy and might still be on the island. Ronan, though skeptical, is shaken enough to agree to the final séance.

After Violet leaves, Ronan attempts a self-serving apology to Marin for his advances, focused on ensuring her silence. He concludes with another predatory proposition, confirming for Marin that he’s unrepentant for his earlier actions. His behavior solidifies her decision. She finds Violet and agrees to help with the plan.