Warning: Contains SPOILERS forSlow Horsesseason 4, episode 1Slow Horsesseason 4, episode 1, “Identity Theft,” has viewers wondering what really happened to River Cartwright (Jack Lowden). Although River has been working for Slough House head Jackson Lamb (Gary Oldman) for three seasons, he still isn’t a veteran MI5 operative — not by a long shot. However, one ofSlow Horses' cast of characterswho is is his grandfather, David Cartwright (Jonathan Pryce).David, who raised and supported him since childhood, is a legendary MI5 agent, having been a major player in the service. Previously, David even opted to destroy the incriminating “Footprint” file, putting MI5’s reputation first.
As evidenced by season 3’s final moments, David and River don’t see eye-to-eye about holding MI5 accountable for its actions. River, who cleverly makes a copy of the “Footprint” file, leaks the information to the public, resulting in some major “First Desk” shakeups. However,MI5’s accountability isn’t the only issue that divides the Cartwright men. In the season 4 opener, River sits down with someone he feels closest to, Louisa Guy (Rosalind Eleazar), and shares that his grandfather’s dementia is worsening. This leads directly to a shocking revelation inSlow Horsesseason 4that has profound implications for the story.
River’s Grandfather Appears To Kill His Grandson In Slow Horses Season 4
David Cartwright Fatally Shoots An Intruder Who’s Later Identified As River Cartwright
When Louisa suggests that River not only care for his grandfather, but put David in a “home,” River balks at the idea — and that’s the last viewers see of the Slough House agent until he’s seemingly shot and killed by his grandfather. Previously, River mentioned that David took a full 10 minutes to realize who he was during their last get-together. In fact, David prattled on about his grandson, thinking River to be a kindly stranger. In reminding viewers of this,Slow Horsesplants the seed that David Cartwright might not be the most reliable narrator.
When “River” breaks character and calls him “gramps,” David shoots and kills the impostor.
On his way home, David is paranoid, muttering that whatever unseen person is following him should reveal themselves. Once inside, River’s grandfather grabs his shotgun and keeps watch until eventually falling asleep in his armchair. David Cartwright is woken abruptly when someone — seemingly River — bangs on his front door.Viewers never get a clear look at River’s faceas he pushes past David to go run a bath upstairs. Feeling something is off, David grabs his MI5-issued panic button and his shotgun. When “River” breaks character and calls him “gramps,” David shoots and kills the impostor.
Jackson Lamb’s Reaction To River’s Death Explained
Lamb Is Strangely Accepting Of River’s Apparent Death (Even By His Standards)
Ahead of its release,Slow Horsesseason 4 was called controversial, and Jackson Lamb’s strange reaction to the incredibly dark opener supports that claim. While Lamb is known to be irreverent, flatulent, and inappropriate, his non-reaction to River’s apparent murder is disturbing. However, Lamb’s actions are also incredibly telling. Even though River’s ID and wallet were found on the body,Emma Flyte (Ruth Bradley), the new Head of the Dogs, calls Lamb to David Cartwright’s home to identify the victim. Disgruntled more than upset, Lamb turns up looking drunk.
…Lamb seems disheveled, suggesting that he doesn’t think the real River is dead.
Once inside, River’s boss carefully goes through the medicine cabinet, looking for something to settle his stomach. Flyte is, understandably, surprised by Lamb’s lack of reaction to the gruesome scene. Blood smears the walls and the victim is so disfigured from the blast that Lamb even cracks a joke about how the body “used to have a face.” Something strange passes over the head of Slough House’s face when he crouches closer to the body, butLamb confirms to Flyte that the victimisRiver Cartwright. Privately, Lamb seems disheveled, suggesting that he doesn’t think the real River is dead.
Slow Horseswas already renewed for a fifth season, which will be based on Mick Herron’sLondon Rulesnovel.
Slow Horses Season 4, Episode 1’s Ending Reveals River Is Alive
River Stopped By Standish’s Before Heading To France
By the end ofSlow Horsesseason 4, episode 1, River is revealed to be alive and well — for the most part. Trusting his gut, Lamb goes to visit the jaded Catherine Standish (Saskia Reeves), who quit Slough House at the end of season 3. When Lamb turns up, Standish is busy looking over newspaper articles about the car bombing that occurred at a shopping center the same night River was killed. Realizing that Standish isn’t asking any prying questions about the circumstances of River’s death,Lamb calls out his former colleague, theorizing that Standish has seen Riverrecently.
David Cartwright […] killed his grandson’s look-alike and then pressed the panic button to alert MI5.
Although Standish initially balks at Lamb’s suggestion, the slovenly MI5 operative says that he saw River’s car parked outside. Standish admits that River did stop by, but that he’s gone now. Meanwhile,Standish is harboring a fugitive: David Cartwright, who killed his grandson’s look-alike and then pressed the panic button to alert MI5. The first episode ends before Lamb can question David, but it does seem like the shopping center incident, which was committed by a man who threatened that his “brothers” would be coming to finish the job, is connected to whatever happened at the Cartwright home.
What River’s Survival Means For Slow Horses Season 4’s Story
River Cartwright Is At The Center Of Slow Horses Season 4’s Strange Conspiracy
WhileRiver’sSlow Horsesstory will be totally differentfrom anything that’s come before, it’s too early to say how, exactly, the River look-alike and the car bomb are related. In episode 1’s closing moments,River sits in the backseat of a cab, riding through the remote French countrysideas he looks at a woman’s passport. Previously, the car bomber’s passport was lying around his apartment, as if he wanted it to be found. Although it’s not evident why River Cartwright is in the cross-hairs, it is clear that he’ll have a connection toSlow Horses' latest conspiracy, setting up another twisty story for the series.
New episodes ofSlow Horsesseason 4 drop on Apple TV+ on Wednesdays through Jun 25, 2025.
The fact that River has seemingly faked his own death suggests thatSlow Horsesseason 4 will feature even more deception than usual. Standish’s apparent involvement, Lamb’s knowledge of the situation, and his conversation with Louisa all recall earlier moments from the series where being in the know is central to the story. While the explosion is certainly the most action-packed aspect of the story, River’s situation may well constitute the narrative heart of the season.
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.
