In the present, Saxon cautions that childhood memories may not be reliable, but he recalls that on the night of the 1961 crash, Peony Lane spent the entire evening with him at Gravesdown Hall teaching him to shuffle cards—American-flag playing cards Edmund had brought back from New York. When Edmund arrived and began shouting at Ford, Peony ushered Saxon to the kitchen.

Saxon then showed Annie Edmund’s silver flask, sealed in a dated police evidence bag. He found it years later in a hidden compartment of Ford’s desk, and the discovery unlocked a suppressed memory: He had witnessed Ford slip several white pills into Edmund’s open flask while Edmund’s back was turned. He had the flask examined, and the analysis confirmed residual pill traces in the flask.

Annie speculates that Ford’s drugging of his brother contributed to the crash. Saxon believes Ford only intended to incapacitate Edmund so that the police could be called, and he chased after the car once Edmund drove off. Annie realizes Frances deliberately obscured these events in her diary to protect Ford. Saxon tells Annie to keep the diary and that he will seek her out when he wants it back.

As Annie arrives back at Gravesdown Hall that evening, Crane calls to warn her that officers are on their way to question her about Samantha’s murder. The evidence is significant: Security footage at the station captured Annie handing Samantha the water bottle later found to contain the fatal concentration of lead that killed her, and hair and fibers from Samantha’s body were recovered from the trunk of the BMW Annie has been driving. The search warrant was issued to Archie as the car’s registered owner and executed the previous day without Annie’s knowledge or Crane’s involvement.

Annie insists that the evidence was planted and suspects that hostile testimony from the Foyle family is driving the case against her. When Jenny rushes in to announce sirens approaching up the drive, Annie resolves to run rather than submit to what she believes will be an unfair process under Chief Inspector Marks. She hears the police enter the house and realizes that she had left the front door improperly closed on the way in, allowing police to enter freely. Annie and Jenny escape through the solarium, leaving the crucial file and diary behind. At the tree line, they are surprised to find Birdy waiting for them. She tells them that she has a car nearby and to follow her through the woods.

While hurrying through the woods, Annie confronts Birdy about entering Gravesdown Hall. Birdy admits that she encouraged Annie’s mother to visit the house as cover so that she could retrieve Peony’s file, but she left without it. Annie works out that since Peony spent the entire night of the 1961 crash at Gravesdown Hall with Saxon, she could not have been the fourth passenger in the car—Birdy was. Birdy confirms it.

When they arrive at Birdy’s car, Annie notices a distinctive key ring in the cup holder: an eagle surrounded by American-flag imagery, and she connects it with the design on Edmund’s playing cards. She identifies these as Edmund’s Bentley keys, which had fallen from Samantha’s bag when she died at Archie’s farm. Archie recognized them at the time but had not traced who last held them.

When Annie asks Birdy directly whether she killed the Gravesdowns, Birdy only says they deserved what they got. Annie reasons aloud that Birdy caused the crash by grabbing the wheel, but all the Gravesdowns survived the initial impact. Annie concludes that Archie ran to the village for help and found Eric, who then cut across the field and came upon the wreck. This visibly moves Birdy, who calls Eric the only person who ever protected her from Edmund. She laments that her sister Emily never had such a defender.

Birdy begins accelerating recklessly through the dark. Jenny spots Archie crossing the road ahead, but Birdy shows no sign of stopping. Annie grabs the steering wheel, and the car spins off the road, striking someone running across a nearby field. All three passengers survive. Archie rushes over and reveals the man they hit was Eric, who had been running after him. Annie is horrified, fearing she has fulfilled the fortune’s prophecy by completing the circle.

Annie is convinced that she has killed Eric. When Crane arrives, he tells her that she will not be arrested and mentions that he and Chief Inspector Marks have reached an understanding. Jenny surprises Crane by revealing that Eric murdered Peony Lane. Annie explains the chain of events: the collapse of the old pub exposed the wrecked Bentley, Peony passed by and recognized it, and later saw Eric in possession of the Bentley’s distinctive keys—at which point she theorized he had been the one to let Olivia out of the trunk and kill the Gravesdowns.

Annie then receives a call from her mother and confronts her about letting Birdy into Gravesdown Hall. She hears a man’s voice in the background. Her mother admits that she has rekindled a relationship with Sam Arlington, Annie’s long-absent biological father, who recently came back into her life. Annie is immediately suspicious, viewing his reappearance—so soon after her inheritance—as no coincidence. She refuses to meet him and, after hanging up, resolves to investigate Sam herself, embracing her aunt Frances’s approach to uncovering dangerous secrets.

In a diary entry, Frances Adams reflects that some mysteries are emotional rather than concrete, and Archie Foyle will always be her unsolved emotional mystery. During the drive back to Castle Knoll, it becomes clear that they want fundamentally different futures: He seeks a simple life on the farm, while she wants education and the wider world. The gap deepens when Archie dismisses her belief in Peony Lane’s fortunes as a phase and tells her that university is an unaffordable luxury for people in their position. When Frances suggests they travel through Europe as an alternative, he laughs it off. She tells him she has realized she was using him as a way of avoiding her own ambitions. Archie is saddened but not surprised. They share a final, deliberate kiss, both understanding it is goodbye.

In the present, Annie questions Birdy before entering Eric’s hospital room. Birdy confesses that she was still inside Gravesdown Hall when Eric killed Peony. When Annie and Jenny arrived, Birdy hid in the pantry and watched through a gap in the door. To protect Eric, she recovered the dagger from the kitchen sink and inserted it into Peony’s body to obscure forensic evidence, accessing the body via the hidden path through the solarium. She then slipped out through a rarely used boot-room door while Annie and Jenny were distracted by the approaching police.

Inside Eric’s room, with Archie present, Eric confesses to all five murders: Harry, Edmund, Olivia, Peony, and Samantha. He admits creating the false harassment call logs by using Samantha’s unlocked computer at the police station.

He then describes the night of the 1961 crash: He arrived to find Edmund, Harry, and Olivia injured but alive, and killed all three with a fallen tree branch. Ford arrived moments later and felt implicated through the drugged flask. He agreed to cover for Eric but demanded Eric keep the Bentley keys as perpetual leverage. When Peony later recognized those keys and realized their significance, she placed the dagger in Eric’s farmhouse door as a message; he threw it in the river, where the waterwheel inadvertently returned it. After Samantha found the keys in his glove compartment, he poisoned her water bottle. Eric explains that he tried to frame Annie because he saw her investment in Archie’s business as Gravesdown money reasserting control over the Foyle family.

Archie explains that when Samantha collapsed on his farm, he panicked and hid her body, wrongly believing that Birdy was the culprit. Annie acknowledges that she had unknowingly left the solarium door unsecured that morning, which allowed Peony to enter and gave Eric the opening to follow her inside. The full picture is now clear.

In a June 1, 1967 diary entry, Frances notes that she and Archie have quietly finalized divorce papers. She tried to return the ruby ring; he refused, so she stored it with her crash-investigation notes. Working at her family’s bakery, she has secretly applied for a women’s scholarship to study psychology at University College London, and the pending application makes her days feel less confined.

Ford visits the bakery and asks if they can be friends again; Frances agrees. When he inquires about Peony Lane, Frances lies and says she never found her, having privately decided to leave the secrets of the crash undisturbed. Ford mentions a newfound interest in fortune-telling, and Frances speaks of her own compulsion to pursue the truth. Ford suggests they go for a walk that evening, and Frances accepts.

That autumn, Annie has the solarium fully restored to displace the memory of Peony’s murder. She reflects that she functions as a “solver of crimes” in the same house where Frances was a “collector of secrets”—a partnership across time (299).

At Christmas, Annie hosts a party in the renovated space. The guests include Jenny and her brother Wes; Detective Crane; Chief Inspector Marks; Archie; Beth; Miyuki; Annie’s mother; her grandfather John; Frances’s former lawyer Walt Gordon; and the village GP, Dr. Owusu. Saxon and Elva decline. Birdy—cleared of involvement after Eric denied she had witnessed any of his crimes—stays home, unwell.

During the evening, Archie confirms that the wrecked Bentley has been scrapped. He tells Annie he believes in luck but not fate, and he admits that he removed four of Frances’s diaries from the Hall in October and will return the ones he still has. When Annie asks why the Foyle family was not part of the inheritance dispute, Archie explains that he and Beth asked Frances to exclude them years ago, viewing Gravesdown money as cursed.

After the guests depart, Annie finds the stack of undelivered fortunes from Peony Lane’s house still in her coat pocket. On impulse, she selects one at random and opens it. It is her own.