Warning: Contains SPOILERS forSlow Horsesseason 4, episode 1.Aptly titled “Identity Theft,“Slow Horsesseason 4’s opener picks up where the show’s third season left off. An adaptation of Mick Herron’sSpook Street, the fourthSlough Housenovel,Slow Horsesseason 4’s storyputs River Cartwright (Jack Lowden), one of Slough House’s newest inductees, and his grandfather, MI5 legend David Cartwright (Jonathan Pryce), in the cross-hairs of a vast — and potentially very personal — conspiracy. At the end of season 3,River brings the “Footprint” file to his grandfather, who suggests they destroy the informationbefore damning evidence about MI5 was leaked to the public.
Knowing that his grandfather will put MI5’s reputation first, River makes a copy of the file to leak. The fallout sees Ingrid Tearney (Sophie Okonedo) forced to resign from MI5 — a move that finally allows Diana Taverner (Kristin Scott Thomas) to secure the highly sought-after “First Desk” position. Elsewhere, Jackson Lamb (Gary Oldman) breaks another hard truth to Catherine Standish (Saskia Reeves), who spent the bulk ofSlow Horsesseason 3abducted. Ultimately,a devastated Standish resigns from Slough House. All of these revelations tee up excitingquestions forSlow Horsesseason 4 to tacklealongside new schemes.
10An Explosion Rocks West Acres Shopping Center
Slow Horses Season 4’s Opening Minutes Are Interrupted By A Violent Act
Slow Horsesseason 4 could be considered a Christmas watch, if only because Roddy Ho (Christopher Chung), Slough House’s IT whiz, is waiting for his co-workers to show up to a holiday party. After phoning the bulk of his teammates, Roddy gets Louisa Guy (Rosalind Eleazar) on the line, who points out that Slough House would never have an office party and, if Jackson Lamb ever did organize something like that, it most certainly wouldn’t take place at a fast-food fried chicken joint. After Louisa hangs up on him,Roddy leaves with his headphones and a bag of leftovers.
The intelligence agency has identified the perpetrator as Robert Winters…
Behind him, an explosion rocks the city. In typical Slough House fashion,Roddy only realizes something is amiss when passersby start running and screaming. The show then cuts to the scene of the crime: West Acres shopping center. According to MI5 intel, the car bomber drove into the mall, possibly as an act of death by suicide. The intelligence agency has identified the perpetrator as Robert Winters, an IT consultant who’s something of a ghost. However, that’s far from the only shocking development inSlow Horsesseason 4’s controversial openingmoments.
9Claude Whelan Is First Desk At MI5
Diana Taverner Was Just A Temporary Stand-In
When First Desk arrives at West Acres, it’s revealed that Diana Taverner didn’t land the permanent Director General of MI5 position after all. Instead, she filled in temporarily in the wake of season 3’s massive MI5 revelations – creating an immediate tension, given her obvious ambition.
The new agency head is Claude Whelan (James Callis), who doesn’t seem to be the most qualified or competent choice, especially in comparison to Taverner.Whelan even suggests Taverner continue attending some meetings in his steadbecause she’s a more familiar face. It’s hard to say if Whelan will last, but, then again,Slow Horsesisn’t always accurate with its MI5depiction.
8River Tells Louisa About His Grandfather’s Dementia
Louisa Encourages River To Bring David Cartwright To A Facility
River and Louisa stop by a pub during their lunch break to have a drink. At first, they discuss Slough House, with River suggesting that they’ll be out of the MI5 purgatory by this time next year. Louisa, on the other hand, is “always” thinking about quitting.
Louisa wrongly assumes River wants to ask her out, but he actually reveals that he’s worried about his grandfather, David, who’s showing signs of rapidly progressing dementia. Since it took David over 10 minutes to recognize the grandson he raised,Louisa suggests River stop by and discuss putting his grandfather in a facility.
7David Cartwright Shoots River
David Doesn’t Believe The Intruder Is His Grandson
Slow Horsesseason 4 picks upwith David Cartwright, a former MI5 legend who’s definitely showing signs of dementia. On his way home, David shouts at an unseen person that he thinks is tailing him. Once inside, David falls asleep in an armchair with a shotgun lying across his knees.
When he comes to, it’s dark and River is, seemingly, banging on his front door. David lets his grandson inside — but something seems off. In the bathroom, David approaches with his shotgun. Upon hearing River say “gramps,“David declares the man isn’t River and shoots him in the head.
6Jackson Lamb Identifies River’s Body
Emma Flyte Calls Upon Lamb, Who Doesn’t Seem Too Upset At The News
Emma Flyte (Ruth Bradley), the new Head of the Dogs at MI5, calls Jackson Lamb to David Cartwright’s house. Evidently, the former agent had pressed a panic button, alerting his former employer that something had gone wrong. When Flyte arrived, her team found River’s body in the upstairs bathroom. Flyte explains that they found River’s ID and wallet on the body, but that they want to go through the formality of having someone close to the victim identify his remains. In typical Lamb fashion,Jackson makes jokes about the situation, noting that identifying a face-less body is hard.
…Lamb’s cool-as-a-cucumber approach is the first major red flag that, perhaps, the body isn’t River Cartwright’s.
There’s no denying that Jackson Lamb’s reaction to the crime scene is strange. Apart from David Cartwright’s confused reaction — he goes from saying the man isn’t River to bemoaning what he’s done — Lamb’s cool-as-a-cucumber approach is the first major red flag that, perhaps, the body isn’t River Cartwright’s. (Of course, the episode title definitely hints at that too.) Regardless of what he’s really thinking,Lamb tells Flyte that itisRiver. On his way out, the ever-rude and flatulent Lamb continues to give Flyte the cold shoulder.
5Emma Flyte Is Tasked With Finding David Cartwright
Cartwright Senior Has Been MIA Since Pressing His Panic Button
Emma Flyte, Duffy’s replacement, is immediately tasked with a tall order: tracking down David Cartwright, who’s been missing in action since seemingly killing his grandson. Jackson Lamb doesn’t offer Flyte much in the way of help, though he does remind viewers (and Flyte) that David gave him a job once.
SinceFlyte is an outsider, hand-picked by Whelan, she’s at something of a disadvantage when it comes to the tight-knit and history-boundagents that compose MI5 (and Slough House). Nonetheless, her quest to find Cartwright senior seems to be one ofSlow Horsesseason 4’s big arcs.
4Robert Winters Mentions His “Brothers”
The Car Bomber Threatens More Violence From An Apparent Network Of Terrorists
In a pre-death video, Robert Winters recorded himself talking about his aims in rather vague terms. The terrorist makes veiled threats about what’s to come, but it’s difficult to glean any real clues from the video. One line does stand out:Winters says that his “brothers” are coming to continue the job he started, suggesting that there’s a network of terrorists out there who are waiting to strike.
Slow Horseshas already been renewed for a fifth season.
When the Dogs raid Winters' apartment, a forensics expert sets off a booby trap rigged with grenades, which really throws Whelan and Taverner for a loop. As if it wasn’t already clear, this scene lays plain thatSlow Horsesseason 4 contains many complex layers that need to be unfolded.
3Slough House Grapples With The News Of River’s Death
Roddy Ho Packs Up River’s Belongings While Louisa Feels Guilty
At Slough House,Slow Horses' cast of charactersare adapting to life without Standish. Moira Tregorian (Joanna Scanlan), who was banished to Slough House by Whelan, isStandish’s temporary replacement, though she already has a hard time imagining how she’ll keep the dysfunctional office in order. Of course,Moira’s demotion isn’t the only change at Slough House.When Roddy Ho starts disconnecting electronics from River’s desk, the rest of the team asks him what’s going on. Roddy explains that Jackson Lamb texted him and revealed that River had been killed by his grandfather the night before.
Louisa fears that she has steered River in the wrong direction…
As Roddy packs up River’s belongings, Louisa clutches her head in despair.Louisa Guy feels personally responsible for whatever happened between River and his grandfather.Based on her earlier conversation with River, Louisa fears that she has steered River in the wrong direction by suggesting he stop by his grandfather’s house at night. No one says much of anything to quell Louisa’s guilt. With his signature impeccably bad timing, Roddy mentions that he has a girlfriend, which is a spot of bright news — though his colleagues don’t necessarily feel the same way.
2Lamb Visits Standish Who Is Housing David Cartwright
Standish Initially Lies To Lamb About Knowing River Is Still Alive
Perhaps hoping to prove his hunch right, Jackson Lamb heads to Standish’s house to learn more about David and (the real) River’s whereabouts. When Lamb arrives, Standish is looking over newspaper articles about the bombing; clearly, the MI5 operative hasn’t completely given up on her former line of work. Standish seems annoyed by Lamb’s arrival, butJackson keeps pressing his former colleague for information, suggesting that she’s hiding David Cartwright. Standish evades Lamb’s line of questioning until he points out that she’s not doing a very good job of lying about what she knows.
After 3 Seasons, Slow Horses Really Needs To Finish Its Biggest Unresolved Story Arc
Slow Horses has expertly expanded its narrative over three seasons, but one particular arc really needs to be resolved before it becomes stale.
“You’re not in shock at River being alive because you’ve seen him,” Lamb says after laying out his theory about the dead person in David’s bathroom being an impostor. When Standish tries to double down,Lamb shrugs her off and points out that he saw River’s car parked outside. Unable to lie any longer, Standish admits that River did stop by, but that he’s gone now. Meanwhile, David is fast asleep in Standish’s bedroom. Lamb bursts in to ask David Cartwright more about what happened between him and the River look-alike, butSlow Horsessaves the conversation for episode 2.
1River Is Alive In Slow Horses Season 4, Episode 1’s Ending
The Slough House Agent Is In France On A Mission
While Jackson Lamb’s conversation with Standish confirms that the real River Cartwright is alive, the ending ofSlow Horsesseason 4, episode 1, hammers home this fact. The show cuts to the French countryside.River sits in the backseat of a cab, looking at a woman’s passport.
New episodes ofSlow Horsesseason 4 premiere on Apple TV+ on Wednesdays through July 31, 2025.
The driver assures him that they don’t have too much further to go until they reach their destination. Although River’s look-alike and the shopping center bombing seem unrelated at first, the ending of the first episode suggests that the two incidents might be linked as more ofSlow Horsesseason 4 unfolds.
Slow Horses
Slow Horses follows a dysfunctional team of MI5 agents led by the notorious Jackson Lamb. Set against the backdrop of the espionage world, the agents must navigate complex operations and defend England from sinister forces, all while dealing with internal struggles and their abrasive boss.
