By Asro 
SPOILER ALERT: The following article contains major spoilers for the Season 6 finale of the Apple TV+ espionage thriller "Slow Horses." If you have not yet finished the season, proceed with caution.
The world of Mick Herron’s Slow Horses has never been a place where happy endings go to retire. It is a bleak, bureaucratic purgatory populated by disgraced MI5 agents, bitter alcoholics, and the occasional genius whose career imploded under the weight of a single mistake. Yet, even by the show’s gritty standards, the conclusion of Season 6—which aired this past Wednesday—has left audiences reeling.
Following a season defined by high-stakes chases, Russian assassins, and a mounting body count, the finale delivered a final, gut-wrenching twist that has ignited a firestorm of speculation regarding the future of the series’ most prominent protagonist.
A Season of Losses: The Ledger of the Fallen
Before addressing the ambiguity of the finale’s final seconds, it is necessary to account for the human cost of the season’s narrative arc. Led by the irascible, chain-smoking Jackson Lamb (Gary Oldman), the Slough House team has been thinned out significantly.
The season saw the tragic departure of Coe, played with a haunting intensity by Tom Brooke. Coe’s exit was a masterclass in tension, culminating in a visceral knife fight that underscored the character’s courageous, if ill-fated, nature. Additionally, honorary "Slow Horse" Emma Flyte (Ruth Bradley) met a grim end, serving as a stark reminder that in the world of MI5, proximity to Lamb rarely guarantees survival. These losses were punctuated by the deaths of numerous adversaries, including a pair of Russian hitmen and several British mercenaries, all of whom found themselves on the wrong side of the Slough House machine.
The Return of Sid Baker and the Illusion of Romance
Season 6 offered a glimmer of hope with the return of Olivia Cooke’s Sid Baker, a character long presumed dead since the series’ debut. Her reappearance, while long-anticipated by readers of Herron’s source material, injected a new dynamic into the life of River Cartwright (Jack Lowden).
The chemistry between the two provided a rare, tender subplot. However, viewers familiar with the show’s cynical DNA knew better than to expect a fairy-tale resolution. As director Adam Randall revealed in an exclusive interview with Variety, a more traditional, "happier" ending was filmed for the pair but was ultimately discarded. The creative team opted instead for a sequence that juxtaposed the intimacy of a potential reunion with the cold, crushing reality of the espionage life.
The Finale: A Breathless Conclusion
The final moments of the season are as deceptive as they are shocking. Cartwright returns to the sanctuary of his deceased grandfather’s home, buoyed by the knowledge that Baker has evaded both Russian assassins and the internal "dogs" of MI5. As Baker takes a shower upstairs, Cartwright, distracted by the mundane domesticity of choosing between tea or wine, suddenly collapses. The season fades to black with him on the floor, gasping for air—a victim of a nerve agent he inadvertently touched earlier in the episode.
This cliffhanger, paired with a teaser for Season 7 in which Lamb cryptically mentions a "postcard from the afterlife," has led many to speculate that Cartwright has been written out of the show. Rumors have only intensified due to widespread reports that Jack Lowden is currently in the running for the coveted role of James Bond.
Behind the Lens: Adam Randall on Production and Logistics
Directing the finale presented a unique set of logistical nightmares. Speaking to Variety, director Adam Randall offered a candid look at the challenges of filming the climactic beach sequence.
"Trying to make sense of the geography on screen was the main thing," Randall explained. "It’s all well and good on paper, and then you can never find a location that’s going to fit and make sense in the way that someone’s imagination can." The team eventually relied on a combination of location rewrites, visual effects, and clever set dressing—such as adding artificial cliffs and tall grass—to explain why the characters were trapped in such a vulnerable position.
The iconic pipe sequence, which provided a claustrophobic, high-tension backdrop for the finale’s confrontation, was an entirely constructed set. Randall noted the immense difficulty of shooting within the pipe, citing the shifting sun as a constant adversary that dictated the shooting schedule and limited the camera coverage.
The "Shake Shack" Mayhem: A Study in Chaos
One of the season’s most memorable moments occurred at a Shake Shack, where Lamb and the young computer genius Reece (Lenny Rush) managed to outmaneuver the villainous Frank Harkness (Hugo Weaving).
Randall described the sequence as one of the most difficult to choreograph. "It needed to create such a sense of chaos that you completely bought that Lamb and Reece could just walk out of there," he said. To achieve this, the production encouraged the extras to lean into the mayhem, with writers Mark Denton and Jonny Stockwood providing a list of inflammatory insults for Lenny Rush to shout at the antagonist. The result was a controlled explosion of noise and confusion that allowed the two characters to escape in plain sight.
The Creative Decisions Behind Coe’s Exit
The death of Coe remains a point of contention for some fans who questioned his decision to enter a confrontation solo and armed only with a knife. Randall defended the creative choice, noting that the sequence was an homage to the source material while serving as a final act of bravery for the character.
"There was never a question about why he would follow him in, because I think it’s a courageous thing to do," Randall stated. To heighten the impact, the production chose to intercut the fight with scenes of River Cartwright attempting to open a snack packet—a quintessentially "Slow Horses" moment that prioritized irony over conventional action-movie tropes.
Implications for Season 7 and Beyond
While the internet is ablaze with theories regarding River Cartwright’s fate, the reality is likely more complex. Production on Season 8 is already underway in London, and Lowden has been spotted on set. Furthermore, fans of Herron’s novels are well aware that the character’s journey is far from over.
Randall acknowledged the frustration of the current ambiguity but remained tight-lipped regarding the specific narrative trajectory. He did, however, confirm that the dark nature of the finale was a deliberate choice to set up the stakes for the next installment.
"We had two endings," Randall admitted. "One was a really lovely, Spielberg-ian, magical end for River’s journey. Had it been the end of the series, it would have been perfect. But we knew, from the book and the next story to tell in Season 7, that we needed the other version."
Regarding the casting rumors surrounding Lowden and the James Bond franchise, Randall kept his cards close to his chest. "I only genuinely know what everybody else knows, which is that he’d be great, and that I think he’s in contention. But I don’t really know, and he can’t say anything."
Final Reflections
As the dust settles on Season 6, Slow Horses remains a rare beast in modern television: a show that respects the intelligence of its audience while refusing to coddle them with easy answers. Whether River Cartwright is truly in danger or merely caught in the latest of many webs woven by Jackson Lamb, the show continues to deliver a masterclass in character-driven tension.
For now, the surviving members of Slough House must soldier on, their glasses raised—not to any one individual, but to the collective weight of their losses. As Lamb knows better than anyone, in the world of MI5, the only thing more dangerous than the mission is the memory of those who didn’t make it back.
Siti Muinah 
Ammar Sabilarrohman 
Layla Zulfa 