Strike learns that, like Jim Todd and Larry McGee, Wade King is a former long-distance lorry driver. Arriving at the Goring Hotel, Strike notices that Robin is not wearing an engagement ring, and she tells him that her house-hunting is on hold. Lord Branfoot arrives, accompanied by Kim.

Kim has disclosed the details of the silver vault case to Lord Branfoot and suggests that the detectives have exploited Decima’s fragile mental health and endangered an infant by failing to disclose that she had a baby. Branfoot implies that he will go to the press with these claims unless they stop investigating the identity of the body in the vault.

Strike correctly guesses that Lord Branfoot has obtained intimate footage of Kim without her consent. Kim looks horrified as Strike surmises that she met a handsome acquaintance of Branfoot’s who took her to a flat on the Black Prince Road. Strike also tells Branfoot that Danny is alive and has already spoken to the press. Branfoot storms out of the restaurant, leaving Strike to confront Kim. Strike threatens to ruin Kim’s reputation if she discloses any further information she gained while working at his agency.

After Kim leaves, Strike shares his theory with Robin that Wade King, Larry McGee, and Jim Todd were all lorry drivers for a sex-trafficking operation.

Strike sleeps poorly as images from the Islamic State videos merge with his memories of the explosion in which he lost his lower leg. The next morning, he travels to Heberley House, Charlotte’s childhood home, where her mother, Tara, still resides. The country estate now belongs to Sacha. Strike intensely dislikes Tara after witnessing her consistent cruelty toward her daughter.

Strike gains entry to Heberly House by telling the housekeeper he is delivering a Cartier necklace to Tara. When the housekeeper leaves to fetch Tara, he heads to the drawing room, confirming his suspicions. The stolen silver nef is displayed on the sideboard.

Strike threatens to report Sacha for receiving stolen goods unless Tara answers his questions. She confirms that Rupert asked her to buy the nef, and she couldn’t resist acquiring an item stolen from her ex-husband. She gave Rupert 6000 pounds and used her contacts to secure him a job abroad at a Clairmont hotel. She insists she does not know where Rupert is currently working.

Decima refuses to believe that Rupert is alive, but Strike insists that he cannot take any more of her money, and the case is closed.

Robin struggles to accept that the William Wright investigation is over. She also feels unsafe and unnerved by the knowledge that Wade King is out on bail. Returning from the office, she panics when two men emerge from the apartment block building, shouting. One of the men is Wade King, who runs away. Robin realizes the second man is her younger brother, Martin. Martin explains that Carmen has thrown him out, and he was waiting on the stairs for Robin when he saw King outside her front door. He shows her a piece of paper, printed with a gorilla’s face.

Martin reveals that he accused Carmen of having an affair when he came home to find her ex-boyfriend in the house. Martin says that Carmen’s ex-boyfriend owns a skip hire business called Excalibur and flaunts his success. He even has his company logo printed on his home gym equipment. Robin convinces Martin that he overreacted and should apologize to Carmen.

Robin calls Strike’s half-sister, Prudence. She asks Prudence to recommend a therapist who will not advise her to give up her job.

At the detective agency, Strike reveals Plug and his associates have been arrested, and Plug’s teenage son is now in the care of his great-uncle and grandmother. Strike also announces that he has decided to continue the silver vault investigation by funding it himself. Relieved, Robin tells Strike her theory that Oz removed William Wright’s weights from his flat because they were customized with something that gave away his identity.

Strike and Robin rewatch the video footage of the delivery to Ramsay Silver. Strike points out that Todd and Wright struggle under the weight of the largest crate as they carry it to the vault. However, when Pamela checked its contents, the crate contained only a few misdelivered items, which she handed to Wright in a bag. Strike questions why the crate appeared to be so heavy.

Murphy calls Robin, revealing that there has been a terrorist attack on Westminster Bridge. Robin panics, recalling that Strike is working in that area of London. When Strike confirms he is safe inside a pub, Robin wonders if she would have felt equally terrified if she thought Murphy had been caught in the attack.

Rena Liddell is discharged from the hospital, and Strike arranges to meet her at The Engineer pub. On the way, he reflects with embarrassment on his instinctive reaction to the Westminster terrorist attack. When he heard people screaming, he was transported back to Afghanistan and charged into the street wanting to intervene. A policeman shouted at him to get back inside the pub.

Rena has already left The Engineer when Strike arrives, and the bar staff informs him that she was shouting and causing a scene. Strike eventually finds her huddled under a bridge of the nearby canal. He is forced to disarm Rena when she pulls out a gun that turns out to be a replica. Rena says she met Niall at The Engineer, and he vowed to take revenge on behalf of her brother, Ben. Rena shows Strike the silver checkered necklace Niall gave her for protection. Niall had a heavy briefcase chained to his wrist when they met, which she believed was full of silver, and he said he would leave it for her under a bridge. Recognizing that Rena is unhoused and unwell, Strike pays for her to stay in a Travelodge.

Midge speaks to Hussein Mohammed, one of William Wright’s neighbors, and sends Robin an audio file of their conversation. Mohammed says that Wright helped him and his wife with their daughter’s wheelchair on a couple of occasions. Wright claimed his girlfriend was pregnant and would soon be moving in with him. On one occasion, Mohammed knocked on Wright’s door to ask if he had taken delivery of a parcel. Wright had covered his weights with a sheet, but it slid off, and Mohammed noticed a black lion logo on a yellow background. Mohammed observed that his daughter’s name, Hafsa, means “lioness cub” in Arabic. Reflecting on this information, Robin searches for the meaning of another name online and is shocked by the results.

Murphy tells Robin he has booked a table at the Ritz for his birthday. Robin feigns enthusiasm while panicking, convinced her boyfriend plans to propose. Meanwhile, Strike lists the items he needs to conclude the silver vault investigation, including multiple sets of handcuffs and Ted’s fisherman’s priest.

Strike explains his plan to Barclay and Wardle.

Robin and Midge meet Kenneth at Ramsay Silver.

Reaching Ironbridge, Strike sends Barclay and Wardle ahead in a hire car to survey the territory. He is pleased to learn that Culpepper has been sacked. Barclay calls to confirm that the coast is clear, as the target has just left with several other men.

Meanwhile, Robin and Midge discover that the wall at the back of the silver vault has recently been reconstructed. Knocking down the bricks, they discover a hiding place full of masonic silver. The space also includes a pile of bloody clothes. They surmise that Jim Todd created the hiding place while working at the store.

Strike uses his skeleton keys to enter Griffith’s house. Hearing a noise upstairs, he realizes he is not alone. Wynn comes downstairs, and Strike sees him talking to a girl through a trapdoor concealed in the floor. Wynn orders the girl to clean herself up as “Mickey wants a go” (848) and will soon be arriving. Strike creeps up behind Wynn and hits him with the fisherman’s priest.

Wynn falls into the basement room below and is knocked unconscious. Strike discovers the imprisoned girl is Sapphire Neagle. She is emaciated, almost naked, and chained to a pipe. As Strike realizes he has no cell reception underground, he hears a group of men return to the house. When Griffiths approaches the open trapdoor, Strike grabs his foot, pulling him into the underground space. The two men fight, and Griffiths slashes at Strike’s face with a knife, almost severing his ear. Barclay and Wade enter the house, claiming to be police officers, and handcuff the guilty men.

Strike produces an old photograph showing Griffiths and Wade King performing in a Belgian club in the 1990s, with Reata Lindvall on the dance floor. From the photo, he deduces that Griffiths led a pan-European sex-trafficking ring using the band as cover, aided by Wade King, Jim Todd, and Larry McGee. During this period, Griffiths murdered Reata, abducted her daughter Jolanda, whom he renamed Chloe, and abused her. Operating under the alias “Oz,” he lured, raped, and killed additional women, including Sofia Medina, and abducted Sapphire Neagle for trafficking.

Griffiths feared exposure when Tyler gave Chloe a violet bracelet that referenced her real name. Realizing Tyler knew her true identity, Griffiths decided to kill him. Believing Tyler was driving in Hugo and Anne-Marie’s car, Griffiths tampered with it, then spread rumors to force Tyler out of Ironbridge. After Tyler was wrongly suspected of involvement in the couple’s deaths, Griffiths—through intermediaries Wynn Jones, Darren Pratt, and Jim Todd—steered him to the website “Abused and Accused.” Todd then encouraged Tyler to flee to London, assume a new identity, and eventually bring Chloe to live with him. With Todd’s assistance, Tyler became William Wright and secured work at Ramsay Silver.

On the day of the murder, Griffiths hid inside a crate delivered to the silver vault. Todd released him, and Griffiths bludgeoned Tyler from behind. He then disguised himself in Tyler’s clothes, beard, and glasses, but tripped on his way out because the shoes were too large. Returning overnight, he mutilated the body to prevent identification and, with Sofia Medina’s help, emptied Tyler’s flat. Strike concludes that Griffiths disposed of Tyler’s belongings and missing body parts in Petts Wood. Afterward, Griffiths murdered Chloe, who was pregnant with his child, and fabricated evidence of her ongoing travels through a fake Instagram account.

As Strike talks, he feels increasingly faint from blood loss. He passes out just as the police arrive.

Niall’s body is found in the canal near The Engineer, after Strike tells the police where to look. Niall drowned after jumping off a bridge with a briefcase of bricks chained to his wrist. The body of Chloe/Jolanda is also found under the concrete floor of Griffith’s basement. Meanwhile, Lord Branfoot goes into hiding after Fergus publishes Danny’s story.

Strike attends Niall’s funeral with his ear heavily bandaged after being surgically reattached. Jade tells him that the code for Niall’s briefcase was the due date for the baby she lost. The briefcase was full of bricks and unreadable papers. Strike suspects that the documents were Niall’s account of the botched SAS operation. Agent Lawrence is also present, and they discuss Niall’s death by suicide. Strike states that he saw a video of an Islamic State execution where a hooded man was thrown from a bridge while chained to a barbell and wondered if the man was Ben Liddell. Lawrence confirms that Ben and Niall were stranded in Islamic State territory when an SAS mission went wrong. As Semple was severely injured, Ben went to fetch water for his friend but was captured and killed. Niall was rescued but was angry about his friend’s death and felt survivor’s guilt. Before he died by suicide, MI5 was trying to ensure he did not disclose state secrets.

Wardle, who has started dating DCI Iverson, confirms that Tyler’s weights and hands have been found in Petts Wood. In her statement, Sapphire Neagle has revealed that Griffiths forced her to call Robin pretending to be Chloe’s friend, Zeta, and Dilys Powell’s great-niece. A curly wig and a ruby necklace have been found in Griffiths’s wardrobe.

Robin arrives at the hotel in Sardinia, where Rupert is working as a waiter. Robin surmises that Rupert left Decima because he discovered she was his half-sister. Rupert explains that Valentine Longcaster was strongly opposed to his relationship with Decima but did not tell him why. However, one night, Valentine was drunk and revealed that his father, Dino, had an affair with Rupert’s mother. Rupert then noticed the physical resemblance between himself, Decima, and Dino, and a DNA test proved they were related. He reveals he went to Sacha’s party to confront Valentine, furious that he did not warn them before they fell in love and Decima became pregnant. He stole the nef from Dino because it belonged to his mother and he felt it was his due. Robin persuades Rupert that Decima deserves to hear the truth from him.

Decima meets Strike and Robin at the agency’s office. Decima states that, although she and Rupert can never resume their former relationship, he plans to return to London and help her raise Lion. When Decima expresses anxiety about telling Lion the truth, Strike suggests that he does not need to know. He asserts that Lion is lucky to have two parents who love him.

Once Decima leaves, Robin declares she is meeting Murphy at The Ritz. As she walks out of the office, Strike hurries after her.

As Robin descends the stairs, Strike calls out, telling her not to “make the same mistake twice” (892). He says he is in love with Robin and wants to marry her. Robin angrily points out that Strike should have declared these feelings when she was single. When Strike reaches for her, she pushes him away, insisting she will not betray Murphy. Robin runs down the stairs, and the door slams behind her. Pat, who has overheard Strike’s declaration, observes that Murphy is handsome, but Robin does not seem happy. She adds that Strike cannot expect Robin to immediately agree to his unexpected proposal.

Strike notices that the black goldfish is again struggling at the tank’s surface. Admonishing the goldfish that it only has itself to blame, he goes to fetch the frozen peas.