After the meeting at MI5 headquarters, Tearney makes Taverner wait before discussing the completed transfer of Virgil-level classified records. Tearney warns that Judd plans to restructure the Service’s command hierarchy by inserting political oversight above the second desks. Tearney suggests an alliance against Judd, but Taverner insists that the Service can weather political interference. When her pager alerts her that River has arrived, she agrees to meet him on the staircase.

River enters headquarters on a visitor pass and tells Taverner a cover story that he is there to consult Webb’s personal records, claiming Webb had given him authorization to turn off his life support if he was unlikely to recover. Taverner agrees to look into it and warns him never to return unannounced. Once Taverner leaves, River mentally prepares himself for the half-hour he has left to complete his mission.

Elsewhere, Marcus and Shirley eat ice cream. Marcus deduces that Shirley has been dumped by her girlfriend and tells her she needs to stay focused as his partner.

At Postman’s Park, the man who had given River his orders, Sylvester Monteith of Black Arrow Security, calls Sean Donovan, who reports that Catherine remains secure at a remote location. Monteith orders Donovan to continue intimidating her. Donovan then calls his colleague Benjamin Traynor, who is guarding Catherine alongside the tattooed young man she has nicknamed “Bailey.”

River returns upstairs, bluffs the security desk, and calls in a false report of an armed man outside to distract security before descending to the records archive. There he encounters Molly Doran, an archivist who recognizes him as one of Jackson Lamb’s agents. River requests a file without authorization; when he recites the file number, Molly reveals that it concerns the prime minister. Before Molly can respond further, security officers come to restrain and arrest River.

At Slough House, Louisa asks Ho to trace Catherine’s phone, but it’s turned off. When Marcus and Shirley return empty-handed, Ho traces River’s phone to Regent’s Park, where the signal is being jammed.

Nick Duffy, head of the Service’s internal police unit, also called “the Dogs,” enters River’s holding cell and interrogates him about the attempted theft. River explains that Catherine has been kidnapped and that he was sent a photo demanding the file as ransom. Duffy dismisses the story, indicating that River should have reported it to Lamb, and knees him in the groin. River recovers enough to insult him, and Duffy punches him in the stomach.

At Slough House, Louisa reports River’s arrest to Lamb. Lamb deduces that the two disappearances are connected and reluctantly calls Taverner, learning that River attempted to steal a Scott-level file and faces handover to police. Lamb warns that Catherine is also missing and threatens to investigate personally; Taverner dismisses his concerns and ends the call.

At the house where she is held, Traynor brings Catherine tea. When she asks if they plan to kill her, he assures her they are not animals. Catherine then mentions the death of a female captain and implies that Donovan was responsible for a fatal drunk-driving crash. Traynor grows somber and leaves.

Tearney travels to meet with Judd. Judd reveals that he hired a tiger team and that Monteith, an old friend of Judd’s from school, orchestrated both Catherine’s abduction and River’s infiltration to expose weaknesses in Service protocols. Judd demands an alliance, explaining his ambition to become prime minister and his need for leverage against the current one: The file that River was sent to steal contains the prime minister’s vetting history. To demonstrate his power over Tearney, Judd orders her to immediately shut down Slough House and dismiss all its agents. Tearney outwardly complies, calculating that proximity to Judd will expose his vulnerabilities.

Lamb searches Catherine’s office, finds an unopened bottle of The Macallan hidden in her desk drawer, and returns it. He tells Louisa he cannot act until he identifies who is behind the operation.

In a car park, Monteith meets Donovan, expecting a celebratory debrief. Instead, Donovan turns hostile and demands to know where Monteith is meeting Judd. When Monteith tries to dismiss him, Donovan slams him against the van. Terrified, Monteith reveals the restaurant where he is meeting Judd in half an hour. Monteith tries to flee. Donovan pursues him.

At the restaurant, Judd waits for Monteith and hears a commotion outside. Police arrive at the scene after witnesses report that Monteith has been dumped from a van. Judd briefly suspects Tearney’s involvement before dismissing the idea, returning to his table, and ordering lunch alone.