Saxon discloses that the keys to the Bentley were never recovered and hands Olivia’s file to Annie. Back in the car with Crane, Annie proposes that a fourth person was in the vehicle, survived the crash, moved Olivia’s body into the road to simulate crash injuries, and then disappeared. She posits that Peony Lane may have been killed to prevent her from naming that person.

Back at Gravesdown Hall, Crane identifies a significant flaw in Annie’s security setup: The front-door camera covers only one of the two large entrance doors. Annie demonstrates that the second can only be opened from the inside once the first door is opened. Crane plans to review the murder-day footage with this in mind. Before leaving, he notes that Annie is improving at separating personal loyalty from investigative suspicion. He says that Frances would be proud—a comparison Annie finds troubling.

Alone in Frances’s file archive, Annie retrieves the filing cabinet keys from their hiding spot inside a ceramic cat, one of the few things she has brought from home. She works through the archive, finding files organized by type of secret rather than by name, with no category for murder. Eric and Birdy’s folders are under “Betrayal,” but both are empty. Archie’s file, which she finds uncategorized in the final cabinet, contains only Peony Lane’s address and a brief handwritten note from Frances telling Archie she keeps his secrets in memory rather than on paper—implying that she always expected him to come looking.

In her 1967 diary, Frances writes that after breaking up with Ford, she finds herself mentally weighing Archie against Ford. When she is in the bathroom, Archie’s date for the evening, a young woman named Samantha, enters. She warns Frances not to believe anything that is said about her. She has a bruised eye, which she insists Archie did not cause. She gives Frances a slip of paper with Peony Lane’s address, saying Archie wanted her to have it. She reveals that she and her boyfriend—a young police constable—are investigating Ford Gravesdown’s role in the crash that killed his brother’s family.

When the constable arrives, Frances watches Ford confront him over his announcement that he is bringing Eric in for questioning. Ford physically retrieves Eric from the police car and sends him away in Ford’s own vehicle. Ford then walks Frances home. They share whisky from a silver flask engraved with his name and the family motto—“Brotherhood conquers all” (154)—and he mentions that an identical flask was made for his brother Edmund. Frances realizes Eric was acting as a police informant on the Gravesdowns, and Ford knew and has just intervened to stop it.

Frances and Archie meet in her family’s bakery, closed for the day. They share leftover pastries while planning a drive to the village of Crownell to find Peony Lane. Frances presses Archie on his estrangement from his brother, Eric.

While they are sitting together on the kitchen counter—a proximity Frances registers as newly charged, quite unlike the measured feeling she had around Ford—Archie explains what happened. After their father left, Eric, trusted with selling the brothers’ one remaining asset, instead wagered it against Ford in a card game and lost it. Archie blames Ford more than Eric, believing that Ford deliberately exploited Eric’s weaknesses. He quotes George Eliot on concealed resentment, suggesting that anger need not dictate action, then proposes that they go looking for some excitement.

In the present, Annie is still unsettled by Archie’s possession of Frances’s diaries. She drives to Foyle Farms to ask for them. In the driveway, she sees a car covered by a tarpaulin. Spotting a triangle of distinctive purple paint under a tarpaulin, she lifts it to confirm: It is the wrecked Gravesdown Bentley, its front crushed and its trunk intact. She calls Crane immediately.

Beth appears from inside the house, and Eric comes out of the garage, where he has been working. Annie has never met him before, but he says that he is working for Archie’s business now. Eric confirms that the car arrived only the day before and explains that in their youth, Archie, Frances, Peony Lane—then known as Ellen and formerly Eric’s girlfriend—and Samantha formed a group to investigate the Gravesdown family. Crane arrives, and Eric reports that Archie is at an out-of-town auto auction.

Inside the farmhouse, Annie discovers that Frances’s diaries have been removed from the shelf. She persuades Beth to try to locate and return them. Eric then volunteers that Peony Lane was paid by Edmund Gravesdown for years to make his bad business disappear, and the car vandalism incident was staged. He grows agitated and refuses to elaborate, and Beth asks Annie to leave.

She goes outside just in time to see Crane force the Bentley’s locked trunk open. The contents cause Annie to scream: Samantha’s body is inside.

Beth and Eric rush outside. Crane secures the scene while Annie breaks the news to Eric, who receives it with quiet devastation. Annie realizes that Samantha must have been killed very recently, as she had spoken with her at the station that same morning. The police arrive, and Annie calls Jenny, who has returned to Gravesdown Hall. She asks her to re-examine Frances’s files for any link between Samantha and Peony Lane. Eric reveals that he drove Samantha to work as usual, and they had lunch plans, but she canceled at the last minute to meet someone else—likely her killer.

Crane asks to accompany Annie home. They head toward Gravesdown Hall, but when Annie sees a road sign for Crownell, she takes that exit instead. Crane reluctantly agrees to let her inside Peony’s cluttered, plant-filled house in exchange for her sharing all her current theories. Browsing the bookshelves, Annie finds a book on bird migration; envelopes bearing various names fall from its pages, and she quietly pockets them. Tucked into a chapter noting that sparrows do not migrate, she finds a folded document: a marriage certificate recording the union of Archibald Lester Foyle and Frances Jane Adams, dated March 6. The year is smudged, but it looks like 1967.

The narrative returns to 1967. Archie and Frances drive through heavy rain. He casually admits that he supplements his income by selling marijuana alongside records at weekend markets. He also admits that he missed the turn to Crownell, and they are heading to Southampton instead. Frances embraces the spontaneity, happy to go anywhere and eager for a life larger than Castle Knoll.

In the present, that evening at Gravesdown Hall, Annie, Jenny, and Crane gather on the library floor to talk about the secret marriage certificate. Annie argues that Frances’s yellow diary, which Archie has, likely contains information he wants suppressed; Jenny suggests that he may simply be protecting something intimate. Crane discloses that Olivia Gravesdown’s ring—a ruby set between two diamonds—was found in an evidence bag attached to Peony Lane’s file, prompting Annie to wonder whether the ruby connects to missing stones from the Gravesdown family dagger.

Reviewing the front-door camera footage, Annie and Crane detect a subtle light shift that indicates that Beth opened the second door off-camera and let someone inside the house. Crane adds that Archie has not been located since Samantha’s body was found.

Annie takes a call from her mother, who mentions that Birdy urged her to obtain Peony’s file specifically because of the ring inside it. This prompts Annie to question whether Birdy returned after disappearing and has quietly been living in Castle Knoll ever since. Recalling that the bird migration book noted sparrows do not migrate, she begins to theorize that Birdy returned to Gravesdown Hall to silence Peony—possibly because Peony intended to confess that the two of them had killed Olivia together decades earlier.

In her 1967 diary, Frances relates her trip with Archie to Southampton. Archie rolls a joint while music plays on his portable radio, and Frances smokes for the first time. They wander a lively outdoor market and eat at an Indian food stall—another first for Frances. As evening arrives, she tells Archie she does not want to go home; she wants days away from Castle Knoll, away from the fate hanging over her. She says she wants to live. Archie kisses her.