Slow Horses

After a serious mistake, caused by a colleague but blamed on him, during a live training exercise at Stansted Airport, MI5 agent River Cartwright is demoted to dead-end work at Slough House, a tranche of MI5 reserved for the agency's screw-ups, headed by the alcoholic and impersonable Jackson Lamb. Lamb assigns River to carry out surveillance on Robert Hobden, a journalist associated with far-right politicians Peter Judd and Roger Simmonds. River discovers that his colleague and officemate Sidonie "Sid" Baker has also been assigned to Hobden, discreetly copying the contents of his USB flash drive in a café. River is then instructed to deliver the drive to the service's headquarters at Regent's Park, much to his surprise.

Hobden makes a series of calls to journalist colleagues alleging he has information that an "attack is imminent". River visits his grandfather, who reveals Hobden was blacklisted when his name appeared on a leaked donor list of the British Patriotic Party, and blamed MI5 for his troubles. He warns River that if MI5 are using Slough House to look into Hobden, it is because there is risk and they want plausible deniability. Lamb's long-suffering assistant Catherine Standish attends an Alcoholics Anonymous meeting. British-Pakistani student Hassan Ahmed is kidnapped by the far-right group Sons of Albion, who announce they will behead him on livestream at sunrise the following day. River breaks rank and leaves Slough House to further investigate.

Hassan's kidnappers – Moe, Larry, Curly and Zeppo – hold him hostage in a London terrace basement, with it transpiring that Simmonds is behind the kidnapping. River, having copied the contents of Hobden's USB drive before delivering it to Regent's Park, realises it contains no information and manipulates a rival, James "Spider" Webb, into confirming the same. Standish begins having flashbacks to the death of a former colleague of hers and Lamb's, Charles Partner. Slough House's cyber expert, Roddy Ho, discovers he cannot hack Hobden's laptop as it is air gapped, furthering everybody's suspicions.

Deputy-Director General Diana Taverner approaches another member of Slough House, Jed Moody, and instructs him to do some "off book" work for her. Two other members of Slough House, Min Harper and Louisa Guy, meet in a pub after work and lament their failed careers. River and Sid decide to tail Hobden, but she confesses that she was assigned to Lamb's team to keep tabs on River. The two see a masked man enter Hobden's home and pursue him, discovering upon entry that Hobden was able to destroy his hard drive with thermite. Hobden escapes as River and Sid fight the masked man, who escapes after shooting Sid in the head.

Sid, alive but in critical condition, is taken to hospital by MI5 security operatives who detain River. Lamb breaks him out, and the two deduce Moody was the gunman sent to kill Hobden. Moody returns to Slough House and attacks Min and Louisa when they re-enter, but is killed when he breaks his neck falling down the stairs in a scuffle. Lamb thinks that Slough House is going to be blamed for whatever operation Regent's Park is running and be disowned if it fails.

Taverner meets with Lamb and reveals Ahmed is the nephew of the second-in-command of Pakistani Military Intelligence. His kidnapping and intended rescue is an unsanctioned false-flag operation masterminded by Taverner herself to potentially increase cooperation with Pakistan as well as neutralise and intimidate the far-right. She claims to have an operative embedded with the Sons of Albion who organised the kidnapping but will also facilitate the rescue. It is also revealed that Standish narrowly escaped a treason charge through her links with Partner and his death.

Hobden meets with Judd and tries to convince him to go public with the information that Hassan's kidnapping is a setup, only to be rebuked. Curly is seen making a series of discreet calls with a burner phone, implying he is Taverner's mole. Hassan tries to escape and is threatened by Moe. Giving him a chance to save face, Taverner offers Lamb's team the opportunity to signal to her man the raid is about to commence, allowing him to escape with Hassan. He, River, Min and Louisa arrive at the property but upon entry discover it empty aside from Moe's beheaded corpse.

It is revealed that Moe (real name Alan Black) was Taverner's mole but was found out and murdered by Curly, who then fled with Zeppo, Larry and Hassan. Driving out of London, Zeppo and Larry reveal that they never intended to go through with killing Hassan and entertain the idea of releasing him, becoming increasingly concerned with Curly's erratic behaviour and rhetoric.

Lamb and his team flee the property before the "Dogs" (MI5 security personnel) arrive, knowing that since the operation has not gone to plan that Slough House will be blamed. River is able to rescue Roddy before he can be taken into custody, but Min and Louisa are unable to stop their colleague Struan Loy from being taken from his home by operatives. Taverner calls Standish several times to flip her allegiance, alleging that Lamb was involved with Partner's death, but Standish remains loyal to Lamb when he comes to extract her. Leaving her house the two are apprehended by James Webb and head of security Nick Duffy, who force them into a car after searching Lamb. En route to Regent's Park, Standish is able to free herself and Lamb after pulling a Glock 17 from her handbag, the weapon having been taken from Moody and placed there by Lamb.

Having discovered the fallout of the failed operation, the Director-General of the Security Service, Ingrid Tearney, pulls out of a State Department meeting in the US and heads back to London, giving Taverner limited time to tie off loose ends. Taverner manipulates Struan into giving false evidence that Lamb was the mastermind behind the false flag operation involving Black, instead of her.

When the team reconvenes, River recalls taking a photo of Taverner covertly meeting with Black whilst carrying out surveillance training. Lamb "returns" Duffy's car to Regent's Park and demands to speak with Taverner, who offers him a way out that would result in his dismissal without charges. She also threatens Standish and says that Sid has died in hospital. Lamb informs her there is a bomb in the car he returned, which allows River to sneak in whilst Duffy's security team investigates.

River confronts Webb, alleging Taverner had him purposefully feed him incorrect intel during the Stansted exercise so he would fail and be demoted, as he had the photograph of her meeting with Black. After locating the photo and evading security, he and Lamb threaten to reveal Taverner's operation to the Director General of MI5 and the press.

Standish and Roddy are able to identify the van being used by the Sons of Albion, as it is linked to a previous cover identity used by Black, and begin to track it. Running out of petrol, Curly announces he still plans to behead Ahmed and die resisting arrest, but Zeppo takes over after pulling a handgun he secretly took from Black's corpse. Hassan tells the group his uncle can offer them money for his safe return. After refuelling, Curly is able to disarm and kill Zeppo, regaining control.

Taverner confronts Judd at his home, revealing that calls he made to his far-right contacts after Hobden's visit resulted in Black's death and the compromise of the mission. Tearney returns from the US, ordering all loose ends be tied up after Taverner further lies to her about the operation. Curly forces Larry and Hassan to a secluded woodland at gunpoint to carry out the beheading. Larry frees Ahmed and attacks Curly with an axe but flees, which enables an injured Curly to recapture Hassan. Larry arrives at the sea port of Harwich but is shot dead by the "Dogs" on the orders of Tearney, who plant a weapon on his corpse to justify the killing.

Curly prepares to kill Hassan outside what he believes is a Norman castle, which Ahmed points out is actually a folly. Lamb, River, Min and Louisa, with assistance from Roddy, are able to track them to the location. Curly and River engage in a brief shoot-out, before the former is knocked out by Hassan with a rock. The Dogs arrive but the group prevent them from killing Curly, in defiance of First and Second Desk.

With the outcome seemingly a success, Roddy tells River that all traces of Sid's name have been wiped from existence, indicating she may still be alive. Hobden is killed by Duffy. It is revealed that Partner was the former Director General of MI5, and officially committed suicide as he was being blackmailed by a foreign intelligence service. Lamb tells Standish he knew and provided the gun, as Partner was a close friend. A flashback reveals Lamb killed him and made it look like a suicide, on the orders of River's grandfather, David Cartwright.

Former field agent Richard Bough, aka Dickie Bow, recognises and follows a man who tortured him during the Cold War, only to die on a rail replacement bus from an apparent heart attack. Jackson Lamb investigates, finding Bough's hidden phone under the seat with the message "cicada", and gets the team at Slough House to look deeper.

River speaks with his grandfather about Bow’s death. David discusses the "cicada" theory of Russian sleeper agents embedded in British society, which MI5 dismissed as a hoax after no sleepers were found, and they concluded that the programme's alleged mastermind, Alexander Popov, did not exist. He tells River that Bow went AWOL in East Berlin and was assumed to have defected, but returned drunk. Bow claimed to have been kidnapped and tortured by Popov, who force-fed him brandy, but was fired. David dismisses River's theory that Bow’s death was the work of the FSB or related to a conspiracy, but warns River to be careful.

Min and Louisa are seconding Webb to provide background security for a clandestine meeting at The Glasshouse between him and Arkady Pashkin, a representative of UK-based energy oligarch and defector Ilya Nevsky. Ho and newcomer Shirley Dander retrieve CCTV footage from the bus and train, showing that the man Bow was following discreetly poisoned him and then took a further train to Stroud in The Cotswolds. River approaches Lamb, revealing that he knows about the cicada conspiracy and is going to Stroud to pursue the matter further.

Lamb meets with Nikolai Katinsky, an ex-KGB agent and defector. He alleges when stationed in East Berlin that he overheard Popov demanding that the cicada programme remain funded after the fall of the Soviet Union. His description of the man Popov was speaking to, Andrei Chernitsky, matches Bow’s killer. River bribes a taxi driver in Stroud, who reveals he drove Chernitsky to an airfield and flying club in Upshott, but was instructed to lie about it and call a number should people come looking. Ho traces the phone to Estonia. Lamb meets with Taverner and convinces her to fund a fake ID and cover package for River, who he then meets and instructs to investigate the airfield and its owner, Duncan Tropper. Taverner is dealing with now-Home Secretary Peter Judd regarding a large anti-capitalist protest in London.

Webb reveals his planned meet with Pashkin to Taverner, who reluctantly approves despite the UK's agreement with Moscow to keep intelligence operatives away from Nevsky, a critic of the Russian government. Min and Louisa meet with Pashkin's security operatives Piotr and Kyril, but the Russians lie about where they are staying. Min covertly follows them back to a commercial address at Edgware Road but is confronted by Piotr, who puts a gun to his head.

The gun threat is a joke, and Piotr invites Min to drink vodka with him and Kyril. The Russians cut the session short when a friend visits. Afterwards Min is killed when he is supposedly struck by a car as he is cycling home drunk. Believing he was targeted also, Lamb investigates the driver, Rebecca, and discovers she previously lived in Vladivostok. He confronts her, and she confesses she was paid off; Min wasn't killed by her car, and she was not driving.

Judd is delivering a speech in the City of London on the day of the protest. For added security, he is to be accompanied by Nick Duffy, leader of the "Dogs", a tactical and security unit, but he demands that Taverner joins him instead. Newcomer Marcus Longridge replaces Min on the Pashkin assignment and confesses to Louisa he has a gambling addiction, which was the reason he was put in Slough House.

Ho, Dander and Standish deduce that Chernitsky never left the UK, and just planted his phone in the luggage of an Estonia-bound touring folk band at the airport. Using his cover as a journalist from The Times, River befriends Kelly, the daughter of the suspected sleeper agent Duncan Tropper. He discovers through her that Tropper and his wife Alex used to be student radicals who moved to the village from London. The family invite him to dinner and introduce him to their visiting friend Leo, who is actually Chernitsky.

Rebecca recounts that Min was attacked and run over by Piotr and Kyril, and finished off by Chernitsky before his death was staged. Lamb discovers Katinsky's involvement as a triple agent; he agreed to assist the Russians and distract Lamb, in exchange for facing no repercussions for his defection decades earlier. Standish speaks with Victor Krymov, the intermediary who set up the meet between Paskhin and Webb. Lamb suggests that Krymov lied about Pashkin being Nevsky's representative, with the younger Russian likely being his competitor.

Dander and Lamb visit Nevsky's residence to find that he shot himself after being poisoned by radiation injection. Louisa meets with Pashkin at his hotel armed with a utility knife, intent on torturing him as she believes he is responsible for Min's death. She is stopped by Longridge. Lamb orders her to temporarily stand down and proceed with the meeting, as Pashkin might resist interrogation. He approaches Regent's Park. Chernitsky leaves the Tropper residence and is pursued by River, who confronts him and Katinsky at the airfield preparing an improvised explosive device. Alex Tropper arrives and explains Katinsky is another friend from university. Then she incapacitates River with a stun gun, so revealing that she is the sleeper agent.

After Alex takes off, Katinsky tells River they plan to fly the plane into The Glasshouse. Duncan and Kelly find and untie River, and he is able to convince them of Alex's true identity. River calls in a "Code September", prompting Taverner to evacuate Judd from his speech at The Royal Exchange and the immediate area around The Glasshouse. Lamb blackmails Duffy to get him into the records department at Regent's Park. He deduces that Katinsky is the spymaster behind the cicada program (passing himself off as a junior bureaucrat when defecting to avoid suspicion) and was the handler of a traitor in the service. Standish beats Krymov in a game of chess and he reveals it was Katinsky, not Pashkin, who he met to set up the Webb meeting. Katinsky specifically requested Lamb's team to be involved.

The meeting between Paskhin and Webb at The Glasshouse proceeds as planned. However, an evacuation alarm activates and Pashkin pulls a gun. Louisa explains to Webb that Pashkin is likely FSB and killed Nevsky. Pashkin shoots Webb and escapes with Piotr, locking the agents inside. Longridge shoots Kyril with a pistol he hid in the conference room. Ho and Dander trace Chernitsky to a train station in central London and pursue him as the evacuations take place.

Louisa interrogates a dying Kyril and learns that Pashkin and his associates were meant to drain Nevsky's accounts from the Glasshouse while it was evacuated. River discovers the bomb left at the airfield and realises the attack was a hoax, calling Taverner to have the Code September retracted. Alex diverts her course, defusing the situation once the Glasshouse has been closed long enough for the heist to take place. Ho notifies River that Chernitsky's destination is Tunbridge Wells, where his grandfather lives.

Chernitsky ambushes Ho on the train but, after Dander boards the train and helps fight him, Chernitsky escapes. Lamb calls Katinsky, deducing that he is the supposedly fictional Russian spymaster "Alexander Popov". Katinsky reveals that he also intended to kill Lamb in retribution for Charles Partner, his mole at MI5. Lamb, already aware, had notified David that he was another potential target due to his complicity in Partner's death. By the time River arrives at Tunbridge Wells by plane with Kelly, David has already ambushed and killed Chernitsky with a shotgun. Louisa and Longridge kill Pashkin when he attempts to escape the Glasshouse, having betrayed and killed Piotr along the way. Realising he has been outmanoeuvred, Katinsky goads Lamb to kill him. Lamb instead leaves Katinsky with one bullet left in his revolver, and Katinsky kills himself.

Taverner and Judd create a cover story for the Code September hoax, blaming it on a security glitch and implicating the prime minister, thereby improving Judd's odds against him in the next leadership election. Lamb asks Taverner to place a plaque for Min with other fallen MI5 agents at St Leonard's Church, but is denied. Lamb and the Slow Horses break into the church and hide a plaque for Min behind a bench. After the rest of Slough House leaves, Lamb adds a handwritten note commemorating Dickie Bow's service as a joe; the note then falls to the floor as Lamb walks off.

Sean Donovan and Alison Dunn are lovers and British intelligence operatives stationed in Istanbul. One night Donovan follows Dunn, suspecting she has stolen a classified file from the British embassy. She loses him during a chase through the city before exchanging the file (labelled 'Footprint') with an unknown man. Donovan soon finds and grieves over Dunn's murdered body. At Slough House, a year later, the team are engaged in their usual tedious tasks. Attending her post-work AA meeting, Standish is befriended by Donovan (calling himself "John" and pretending to be part of the AA group) and they go to a cafe; feeling uneasy after Donovan mentions Lamb, Standish tries to sneak out but is kidnapped by a team led by Donovan. The next day, the slow horses investigate Standish's unusual absence. Shirley and Marcus go to Standish's flat and realise she hasn't been home. Louisa tracks Standish's movements to the cafe, notices that security camera cables had been cut, and finds something of Standish's in a nearby underpass. At Slough House, River is texted a photo of Standish with a gun to her head and the message "Barbican bridge, one minute or she dies."

Telling no one about the message, River races to the Barbican Bridge and meets Webb, acting on behalf of the kidnappers who have threatened his family. Webb instructs River to steal the Prime Minister's vetting file from MI5 headquarters before midday (an hour) or Standish will be killed. River suspects he is the victim of a prank until a sniper's laser-target appears on Webb's chest. River gains entry to the Park by claiming to have found a missing diamond from the Glasshouse incident in Season 2. Meanwhile, Louisa continues to investigate the cafe's surroundings and links an abandoned car to Donovan. Lamb notices Slough House is being watched. Shirley and Marcus follow one of the watchers, but he escapes. Lamb meets with an old associate, Sam Chapman, and establishes that Donovan is employed by a private security firm. At the Park, River evades Nick Duffy, the head of the Dogs (security), and gradually works his way into the records department after stealing a security pass from another Dog, Hobbs. Head of records Molly Doran refuses to help River find the PM's file. Lamb calls, instructing River to get out of the Park immediately, saying that Standish is in no real danger because the kidnappers are from a "tiger team" designed to test MI5 security. River sneaks out of the Park but is later captured by Duffy and his team.

River is given a brutal and vindictive beating by Duffy in revenge for having made the Dogs look incompetent. Lamb discovers that Standish's kidnappers are private security firm Chieftain, a "tiger team" hired by Home Secretary Peter Judd to demonstrate weaknesses in MI5's security. Judd uses the operation's apparent success to strongarm Tearney into privatising MI5's security, giving business to Chieftain, who are run by an old school friend of Judd's, Sly Monteith. Monteith loses control of the situation, however, when Donovan goes rogue, kidnapping Chieftain operative Sturges and taking Standish and Sturges to a new safe house. Shirley and Marcus break into Donovan's house unauthorised and learn about "stage two" of his plan, which is to get hold of MI5's Grey Books, a record of conspiracy theories. The two report this finding to Lamb, who secures River's release from MI5 and sends him with Louisa to Chieftain's headquarters, where they discover that Webb had been working with Chieftain the entire time. Monteith sends Webb to pay off Donovan and secure the release of Standish, but an altercation leads to Donovan accidentally killing Webb. Lamb interrupts Judd and Monteith's dinner at a posh restaurant to try to secure Standish's release. Donovan dumps Webb's body outside the restaurant.

Tearney reasserts control over MI5. She plans to allow Donovan access to the Grey Books in return for Standish’s release and then have him arrested by Duffy. Meanwhile, Sturges escapes from the safehouse, where Donovan reveals that he is working with Alison Dunn’s siblings, Ben and Sarah, seeking justice for her death. Standish sympathises and tells them where they can find the file they are seeking. Meanwhile, Shirley and Marcus are fired by Lamb, and River comforts his grandfather, who is suffering from memory lapses. Roddy locates the safehouse and sets off with Lamb to rescue Standish. River and Louisa escort Donovan and Ben into the file-storage facility, where Ben reveals that the Grey Books were a ruse and that he is seeking a different file. After a conversation with Doran, Tearney deduces that someone in the Park has hidden a particular file inside the facility for Donovan to find. Duffy takes charge of a team of Chieftain mercenaries and is ordered by Tearney to kill everyone inside the facility to ensure the file isn't leaked.

Tearney confronts Taverner, who is revealed to have been Donovan's source, and had left the "Footprint" file in the facility for Donovan to leak, as it contains evidence of wrongdoing that will lead to Tearney's downfall: years earlier she had agreed to test a new device that would wirelessly hack any computer. The failure of the device resulted in multiple near-deaths, the only report on the mishap stored in "Footprint". Alison's plans to leak it to the world were uncovered by Tearney, who sent an operative to kill her and make it look like a suicide.

Chieftain operatives prepare to enter the facility and set up a trap outside of it. River warns Lamb and then calls Slough House, asking for the help of Shirley and Marcus just before Chieftain cuts off the phone lines. Shirley and Marcus arm themselves and drive to the facility, hoping that by helping River and Louisa they may be given their jobs back by Lamb. Chieftain agents storm the building and capture Douglas, the facility's sole security employee, who is ruthlessly executed by Duffy shortly afterwards. Lamb reaches Standish at the Dunn house and rescues her from Sarah, but Sturges and Hobbs arrive with orders to kill everyone at the house. River, Louisa, Ben, and Donovan resist the assault and find the "Footprint" file, but Ben is killed.

Hobbs and Sturges storm the Dunn house, however are outmanoeuvred by Lamb, who rigs the house with booby traps. Sarah strangles Sturges to death after a brief struggle, while Lamb kills Hobbs. Roddy attempts an heroic rescue, crashing a bus through the side of the house, too late to be of any help. Donovan sacrifices himself to allow River and Louisa to escape the file storage facility with the "Footprint" file, and they are rescued from Duffy’s planned ambush by Shirley. Marcus defeats Duffy in a fistfight and Louisa finishes Duffy off with a rock to the head. Lamb tells Standish that her hero, Charles Partner, was a traitor who was using her, leading a devastated Standish to resign from Slough House. River takes “Footprint” to his grandfather, who destroys it, worrying about the reputational damage it will cause to MI5. Anticipating this, River has already made a copy, which he leaks. In the aftermath, Tearney and Judd are forced to resign, with Taverner assuming Tearney’s place as First Desk.

A suicide bomb goes off at the Westacres shopping mall in London, carried out by Robert Winters. After Winters publishes a video confessing to the attack, a police force breaks into his flat, but three of them are killed by a booby trap. River confesses to Louisa that he thinks his grandfather, David, is suffering from Alzheimer's and becoming paranoid. She encourages him to care for David, as David cared for River when he was growing up. Meanwhile, Marcus is struggling to kick his gambling addiction, Roddy claims to have a girlfriend, Standish has been replaced by the seemingly-competent Moira Tregorian, and the PTSD-suffering JK Coe has joined Slough House. At David's house, a man arrives at night, claiming to be River. David shoots and kills him, and then flees. Lamb is called to identify River's body by Emma Flyte, the new commander of the Dogs, and he does. Lamb confronts Standish at her flat and learns that David is sheltering at her house and that River is still alive. River is seen to be alive and in the backseat of a taxi in France.

Having learned that the man David shot was an assassin called Bertrand, River hides David at Standish's flat, assumes Bertrand's identity and travels to the French town of Lavande to investigate. Lamb reveals to the team that River is alive, and unsuccessfully questions a mentally deteriorating David as to why he might have enemies in France. MI5 analyst Giti Rahman discovers that Robert Winters is a "cold body", a fake identity created by MI5. Taverner destroys the evidence and blackmails the new First Desk Claude Whelan into going along with the cover-up. River follows clues to a secluded estate, Les Arbres, and is nearly killed by a mysterious man with ties to both Winters and Bertrand. River is saved by another man, who knocks him out with the butt of his shotgun and takes him captive.

River is held captive by the mother of Bertrand, who reveals that Bertrand’s father Frank Harkness raised several sons by different mothers at Les Arbres and that she blames Harkness for her son’s death. A mob arrives seeking to kill River, thinking he is Bertrand, but he manages to escape. Flyte interrogates Lamb, who gives up David’s location. Standish successfully conceals David from Flyte, but a confused David then runs off. Whelan recruits Giti to investigate MI5’s cold bodies behind Taverner’s back. Lamb learns from Tregorian that David’s bagman, Sam Chapman, had spent time in Lavande 30 years ago, just as Harkness sends Patrice, an assassin, to kill Chapman. Lamb manages to rescue Chapman, with help from Marcus and Shirley, but Patrice escapes.

Chapman tells Lamb how he was sent by David to Les Arbres 30 years earlier to give the mercenary group that operated there a cache of guns, money and “cold body” identities in exchange for a woman. Harkness's employers threaten to have him killed unless he helps them cover up their involvement in Westacres by taking out Chapman and David. Lamb deduces that David has gone to the old MI5 HQ, now a luxury hotel, and manages to extricate him before the Dogs arrive. Attempting to flee the country, Chapman is caught by Patrice and killed after refusing to disclose David’s whereabouts. Whelan discovers that River has travelled to France using Bertrand's cold body identity. As River returns to London, he is chased by the Dogs and escapes to David's house, where he realises that his mother may be connected to Les Arbres, before being caught by Flyte.

David reveals to Lamb and Standish that the woman he secretly had extracted from Les Arbres was his daughter—River's mother—whom he exchanged for the money, weapons and fake identities Harkness used to start a "deniable assassination squad" of killers trained from birth. Lamb leaves to investigate Chapman's disappearance, while having Standish take David to Slough House. Tregorian learns from Ho that Whelan had her sent to Slough House for unwittingly finding evidence that he visits prostitutes. Coe tells Ho that his "girlfriend" Kim is actually a bot. River convinces Flyte to send the photo he retrieved from Les Arbres of Harkness's group to the Park; Giti learns that Harkness is a former Special Forces and CIA operative who was discharged for crimes including embezzlement and torture. Whelan and Taverner link the cold-body identities of Harkness's sons to several previous assassinations worldwide, and plot a cover-up. Harkness breaks into Molly's apartment and forces her to give him her security credentials so he can track the convoy of Dogs taking River to the Park, and sends Patrice to intercept. Patrice kills four Dogs, knocks Flyte unconscious, and kidnaps River.

River is taken to meet Harkness, who confirms River's suspicions that he is his biological father. Harkness offers to train River to be part of his organisation, which River swiftly rejects. The Dogs converge upon River's location at the same time as Louisa and Flyte. Harkness puts a live grenade in River's sweatshirt; Louisa throws it in the water where it explodes, but Harkness escapes in the chaos. River leads the pursuit to the train station, where Harkness allows himself to be arrested. Meanwhile, Lamb finds Chapman's body where he went to pick up his flight fund; Patrice, who has Chapman's phone, listens to a message left by Tregorian for Chapman saying that David is safe at Slough House. Patrice invades Slough House, killing Marcus before being subdued by Shirley and a returning Lamb. Coe talks Shirley out of killing Patrice, before shooting him dead himself. Harkness negotiates his release by threatening to reveal that MI5 and other security agencies hired his mercenary group to kill their targets over the years, having left letters at Molly's house addressed to Whelan and other heads of service that were set to be uploaded online within 24 hours of his arrest. River has David committed to a care home against his wishes, and is invited by Lamb for a drink, in silence.