Jack Lowden’s Slow Horses Season 6 Finale Leaves Fans Fearing for River Cartwright’s Future

Jack Lowden has found himself at the centre of one of the biggest talking points in British television after the dramatic conclusion of Slow Horses season 6 left the fate of his character, River Cartwright, uncertain.

The acclaimed Apple TV spy thriller concluded its sixth season on Wednesday, 21 October 2026, delivering a devastating final sequence that has raised serious questions about whether Lowden will return for the already-confirmed seventh season.

The Scottish actor, who has portrayed the ambitious but frequently unfortunate MI5 agent since the series began in 2022, faced perhaps his character’s most dangerous situation yet in the closing moments of the episode titled Judgement Day.

While the finale brought several major storylines to a conclusion, it deliberately left River’s survival unresolved, prompting fresh discussion about the character’s future and Lowden’s increasingly prominent position in British television.

The development also comes as the 36-year-old actor continues to be linked with speculation surrounding the next James Bond, although there has been no official announcement connecting him to the role.

For viewers who have followed River’s complicated relationship with Jackson Lamb, played by Gary Oldman, the latest ending represents a significant turning point in a series that has become increasingly willing to put its central characters in mortal danger.

What Happened to Jack Lowden’s River Cartwright in the Slow Horses Season 6 Finale?

The final episode sees River survive a violent confrontation involving Russian assassins and his estranged father, Frank Harkness, portrayed by Hugo Weaving.

However, the immediate danger appears to have passed when River returns to his late grandfather’s house, hoping to reunite with former Slough House colleague Sid Baker, played by Olivia Cooke.

The sequence initially suggests that the pair might finally have an opportunity to develop their relationship after spending much of the season attempting to escape dangerous enemies.

Instead, River unknowingly touches a contaminated crowbar while preparing to open a bottle of wine.

Moments later, he begins experiencing symptoms consistent with poisoning before collapsing onto the floor, struggling to breathe and unable to call for help.

The episode ends without confirming whether he survives.

Speaking to TV Insider following the finale, season six head writer and co-executive producer Gaby Chiappe addressed the uncertainty surrounding his fate.

“We don’t know what’s going to happen to him,” Chiappe explained.

She confirmed that the story had already established the possible use of Novichok, a highly dangerous nerve agent, while emphasising that exposure did not automatically establish whether River would live or die.

The writer also explained that an earlier scene involving the assassins had planted the clues needed to understand the final sequence.

That decision gives the ending an additional layer of significance, with viewers able to revisit previous episodes to identify how the attack was prepared.

Christopher Chung, who plays technology specialist Roddy Ho, also praised Lowden’s performance during the final moments.

Speaking to Radio Times, Chung said: “Jack was fantastic in that scene.”

He described the ending as the show’s biggest cliffhanger, highlighting the unusual uncertainty surrounding one of its longest-serving characters.

Director Adam Randall similarly explained that the extended quietness of the sequence was intentional, allowing the apparent promise of a happy ending to turn into something far more disturbing.

The result is an unusually personal moment in a series more commonly associated with elaborate intelligence operations, political conspiracies and Jackson Lamb’s abrasive humour.

Lowden’s performance places River’s vulnerability at the centre of the drama, rather than relying on a conventional action sequence to close the season.

The finale also delivers other significant consequences for Slough House, including the death of Emma Flyte, played by Ruth Bradley, and a dangerous confrontation involving several members of the intelligence team.

Critics React to Slow Horses Season 6 as Questions Grow Over Jack Lowden’s Return

The sixth season has attracted considerable attention from television critics, particularly following the departure of original lead writer Will Smith and the appointment of Gaby Chiappe to oversee the adaptation.

Writing for The Indian Express, television critic Shubhra Gupta awarded the season four stars out of five, describing it as the “best season of the lot, no notes.”

Her review praised the production’s ability to retain its combination of sharp humour, flawed characters and increasingly dangerous espionage while maintaining the momentum established by previous seasons.

Meanwhile, Nick Hilton, reviewing the programme for The Independent, examined Lowden’s particular appeal as River Cartwright.

Hilton described the character’s recurring “signature dashing incompetence“, reflecting the unusual balance between River’s apparent suitability for traditional heroic roles and his repeated mistakes.

That contrast has remained an important part of the show’s identity.

Unlike the polished intelligence officers typically associated with British spy fiction, River regularly finds himself outmanoeuvred, injured or forced to depend on colleagues whose abilities he initially underestimates.

However, the latest finale has also produced a more divided critical response.

Writing for The A.V. Club, William Hughes questioned whether the dramatic ending and extended action sequences distracted from the character-driven storytelling that helped establish the show’s reputation.

Hughes argued that the cliffhanger interrupted what might otherwise have been a more complete emotional resolution.

The differences in critical opinion underline an important change in the series.

After six seasons, Slow Horses is no longer relying solely on its established formula of cynical office politics, flawed spies and unexpectedly effective intelligence work.

Instead, the programme is increasingly exploring the permanent consequences of the dangerous assignments undertaken by Lamb’s team.

Lowden’s performance remains central to that transition, particularly as River attempts to reconcile his professional ambitions, complicated family history and growing personal attachments.

According to Rotten Tomatoes, the sixth season held a 100% critics’ score from 37 reviews at the time of writing, although audience assessments have been more mixed.

The wider reaction suggests that the show continues to attract substantial critical support, even as viewers and reviewers debate the direction of its later seasons.

Will Jack Lowden Return in Slow Horses Season 7?

Although River Cartwright’s apparent poisoning has raised questions about Lowden’s future, there has been no official confirmation that the actor is leaving the programme.

Apple TV has already commissioned a seventh season, which will adapt Bad Actors, the eighth novel in Mick Herron’s Slough House book series.

A short preview shown following the season six finale offers hints about River’s uncertain position but does not provide a definitive answer about his survival.

Readers familiar with Herron’s novels may recognise elements of the storyline, although the television adaptation has already demonstrated its willingness to change important events and character outcomes.

This means the books cannot be treated as a guarantee of what will happen in the television version.

Apple also announced an eighth season on 15 September 2026, confirming that the drama will continue beyond its next instalment.

That season is set to adapt Herron’s novel Clown Town, with Gary Oldman’s Jackson Lamb and Kristin Scott Thomas’s Diana Taverner at the centre of another major intelligence conflict.

However, the confirmation of further seasons does not independently establish whether Lowden will appear in either instalment.

The continued speculation about his possible casting as James Bond has added another dimension to the discussion, particularly given his experience portraying a British intelligence officer.

Nevertheless, suggestions that River’s cliffhanger has been designed to accommodate a potential Bond role remain speculation rather than confirmed production information.

Apple has not announced an official premiere date for season seven, although a 2027 release is widely anticipated.

For now, all six seasons of Slow Horses are available to stream on Apple TV.

Lowden’s future as River Cartwright remains one of the show’s biggest unanswered questions, ensuring that the aftermath of the sixth season will be closely watched when Jackson Lamb and his dysfunctional intelligence team eventually return.