River chases the wrong target through King's Cross station during a training simulation, and the real target detonates a device.

River Cartwright is exiled to Slough House, a dumping ground for disgraced MI5 agents, after failing his training simulation.

The slow horses gather around Roderick Ho's monitor to watch a video of a hooded young hostage in an orange jumpsuit.

River examines files copied from journalist Hobden's memory stick and finds nothing but the number pi listed to thousands of decimal places.

Jackson Lamb tells the Slough House team that the kidnappers are British white nationalists, not the Islamic extremists everyone assumed.

Sid reveals to River outside Hobden's house that she was assigned to Slough House specifically to spy on him.

A masked intruder breaks into Hobden's property, a violent chase and struggle follow, and Sid Baker is shot in the head.

Lamb arrives at the hospital and frees River before the Dogs can formally question him about the shooting at Hobden's house.

Min and Louisa break into Slough House after hours, encounter a masked intruder, and the intruder falls down the stairs and dies.

Louisa removes the dead intruder's mask to reveal the body is that of Jed Moody, a fellow Slough House agent.

Lamb calls the number stored on Jed Moody's burner phone and secretly meets Diana Taverner, who confesses she orchestrated the kidnapping.

The slow horses arrive at the kidnappers' safehouse to find it abandoned and Alan Black's severed head on the kitchen table.

Lamb creates a false bomb threat inside MI5 headquarters to distract Taverner and her agents while River infiltrates the building.

River retrieves a file from Spider Webb containing a photograph showing Taverner meeting Alan Black, proving she arranged River's exile to Slough House.

Hassan wrests an axe from Curly in Epping Forest, chooses to spare his life, and walks to waiting police on the road.

River Cartwright is exiled to Slough House after failing a pivotal training simulation, joining a team of disgraced MI5 agents under the eccentric Jackson Lamb. When a young British Pakistani man is taken hostage by a nationalist group called the Voice of Albion, the slow horses find themselves unexpectedly drawn into the crisis. A nighttime surveillance of journalist Hobden ends violently when Sid Baker is shot, and a break-in at Slough House exposes the treachery of fellow agent Jed Moody. Lamb confronts Second Desk Diana Taverner, who confesses she engineered the kidnapping as a publicity stunt, but the plan has spiraled dangerously out of control. The slow horses race to rescue the hostage while Lamb and River infiltrate MI5 to expose Taverner's conspiracy with incriminating photographic evidence. The crisis resolves when Hassan Ahmed escapes his captors in Epping Forest, leaving Taverner compromised by the truth of her scheme.

The headline events of the Slough House kidnapping crisis.

Sid Baker poses as a regular customer at journalist Hobden's café, spills coffee as a distraction, and steals files from his laptop.

River secretly removes the memory stick from Hobden's flash-box before delivering the package to James Webb at Regent's Park.

River visits his grandfather David Cartwright, who warns him to take the journalist investigation seriously and avoid rash decisions.

Jed Moody meets his former Dogs supervisor Nick Duffy at a bar and suggests Lamb may be running an unauthorized operation.

Diana Taverner meets Jed Moody and instructs him to remove the bug he planted in Lamb's office and begin working directly for her.

Min Harper and Louisa Guy go to the pub after the hostage video appears, debating what Lamb might know about the case.

Lamb searches Jed Moody's body and discovers a burner phone with only one number programmed into it.

Robert Hobden visits Conservative politician Peter Judd and blackmails him into leaking to the press that MI5 staged the kidnapping.

Taverner proposes sending the disgraced Slough House agents to rescue Hassan, presenting the mission as their chance at redemption.

The kidnappers learn through a press leak that one of their group is an undercover agent, and Curly kills Alan Black.

Taverner reports to her boss Ingrid Tearney and falsely blames Jackson Lamb's team for the botched hostage operation.

Taverner pressures captured slow horse Struan Loy into falsely confessing that the Slough House team was running a rogue operation.

Min and Louisa track down Roderick Ho at his real address, which Ho had secretly altered in the Slough House personnel files.

Roderick Ho contacts his hacker network and breaks into the kidnappers' rental car navigation system to track Hassan's location.

Lamb tells Roderick Ho that the reason he was exiled to Slough House was that he was responsible for an agent's death.

Behind the main crisis, a web of covert activity and betrayal shapes events at Slough House and Regent's Park. Sid Baker steals files from journalist Hobden's laptop while River secretly copies the memory stick before handing it to his rival Spider Webb. Jed Moody plants a bug in Lamb's office and begins informing for Taverner, while Hobden blackmails politician Peter Judd into leaking MI5's involvement to the press. As the operation collapses, Taverner manipulates her remaining assets, pressuring captured agents to betray their colleagues while blaming Lamb's team for her own failures. The remaining slow horses quietly outmaneuver the Service by protecting their addresses, pooling their skills, and tracking the hostage through a network of hackers. In the aftermath, Lamb makes a rare personal disclosure to Roderick Ho, hinting at the guilt and purpose that have shaped his leadership of Slough House.

The secondary operations and betrayals behind the main crisis.

River forces open the flash-box and injures his hand in the process, stealing a copy of Hobden's files before delivery.

Catherine Standish recalls the day she found her former boss Charles Partner dead in his bath, an event she believed was suicide.

Lamb sets a trap for someone following him home at night, but the pursuer turns out to be only a teenager.

Taverner tells Nick Duffy that she personally assigned Sid Baker to Slough House, revealing that Sid was always her planted agent.

River connects the Voice of Albion kidnappers to journalist Hobden's far-right rhetoric, realizing the terror threat is domestic and racially motivated.

Hassan overhears his captors state that the color of his skin was their only reason for choosing him as their target.

Alone in captivity, Hassan silently names his three captors Larry, Curly, and Moe after the Three Stooges to steady his nerves.

River wakes in a locked hospital room and tells Lamb he believes Jed Moody was the person who shot Sid Baker.

Taverner reveals to Lamb that Hassan Ahmed is related to a senior official in Pakistan's intelligence service, dramatically raising the stakes.

Taverner threatens to revive dormant treason charges against Catherine Standish as leverage to force Lamb's cooperation with the rescue mission.

Catherine Standish pulls a gun from her bag and calmly levels it at Spider Webb, allowing her and Lamb to escape custody.

River enters Taverner's office in Spider's clothes and presents the photograph proving she conspired with Alan Black to engineer River's exile.

Hassan regains consciousness after being struck with an axe handle and decides to run into the forest despite his injuries.

In the aftermath, Sid Baker is found to have vanished from the hospital with no records of her existence remaining anywhere.

Lamb reflects alone in his Slough House office, wondering whether he is truly as ready to step away from the spy game as he believed.

Beneath the surface of the kidnapping plot, a series of personal revelations and quiet decisions shape the fate of everyone at Slough House. River steals evidence and uncovers the nationalist roots of the kidnapping, while Hassan holds himself together in captivity by renaming his captors and confronting his fear with dark humor. Lamb's secret meeting with Taverner exposes the leverage she holds over Catherine Standish and forces an uneasy deal between two deeply distrustful players. Catherine Standish, long underestimated by her colleagues, proves her composure by drawing a weapon on the Service's own Dogs, while River infiltrates Regent's Park and finally confronts the woman who sabotaged his career. Hassan's final decision to spare Curly's life rather than exact revenge resolves the crisis on his own moral terms, and the novel closes on absence and ambiguity, with Sid Baker vanished without trace and Lamb quietly reconsidering whether his appetite for the game has truly gone.