Slow Horses Season 6 Review: The Body Count Just Went Up

Filmoria Review

Official key art © Apple TV+, via TheTVDB.

Quick Facts

• Showrunner/Based on: Adapted from Mick Herron’s novels Joe Country and Slough House
• Cast: Gary Oldman, Jack Lowden, Kristin Scott Thomas, Saskia Reeves, Christopher Chung, Aimee-Ffion Edwards, Rosalind Eleazar, Joanna Scanlan, Samuel West, Ruth Bradley, Tom Brooke, Jonathan Pryce, Hugo Weaving, Olivia Cooke, Lenny Rush
• Platform: Apple TV+
• Episodes: 6, released weekly
• Premiere date: September 16, 2026 (finale October 21)
• Genre: Spy drama, black comedy

Slough House Has a Body Count Problem

Six seasons in, most spy shows would be running on fumes. Slow Horses somehow keeps finding new ways to be vicious about its own premise, and season six might be the meanest run yet. It opens with a simple, horrible idea: someone has a list of every agent who’s ever washed out to Slough House, current and former, and they’re working through it methodically, with hitmen who know exactly what they’re doing and superiors at Regent’s Park who can’t be bothered to care. Bodies start dropping in the cold open and don’t really stop, which tells you everything you need to know about the tone this season is chasing.

That’s the trick this show has pulled off better than almost anything else on television right now: it treats its characters as genuinely disposable while somehow making you care more about them with every loss. Jackson Lamb, played with his usual magnificent contempt for everyone around him by Gary Oldman, spends most of the season a step behind, which is unusual for a character who’s normally three steps ahead of everyone in the room, including the audience. Watching him scramble is its own quiet pleasure.

The New Blood Actually Earns Its Keep

Adapting two Herron novels, Joe Country and Slough House, into a single six-episode run is an ambitious swing, and there were reasons to worry going in given the amount of behind-the-scenes turnover this production has weathered. Those worries turn out to be mostly unfounded. Newcomer Lenny Rush slots into the ensemble without a hint of the awkwardness that usually comes with introducing a new face into a cast this established, and the character work around Hugo Weaving’s Frank Harkness gives Jack Lowden’s River Cartwright his most interesting material in years. Their scenes together carry a father-son tension that’s equal parts wounded and dangerous, and it’s genuinely some of the best acting the show has produced.

Olivia Cooke’s return as Sidonie Baker deserves a mention too. She slots back into the group dynamic instantly, no clunky re-introduction scenes required, and her chemistry with Lowden picks up as if no time had passed at all. Kyle Soller and MyAnna Buring, playing the season’s central pair of hitmen, bring a coldness that’s genuinely unsettling without tipping into cartoon villainy. They’re professionals doing a job, which somehow makes them scarier than if they were sadists enjoying it.

Writing That Still Refuses to Play It Safe

What keeps this show ahead of its many imitators is the writing’s refusal to protect anyone. Characters you’ve spent five seasons growing attached to are treated as expendable the moment the plot calls for it, and the show never signals in advance who’s safe. That unpredictability, paired with dialogue that’s consistently the funniest thing on television not trying to be a comedy, is the engine that’s kept this franchise running long past the point most spy dramas run out of ideas. Christopher Chung’s Roddy Ho gets a handful of scenes this season that manage to be simultaneously pathetic and weirdly moving, which is a tightrope walk few shows would even attempt.

Kristin Scott Thomas continues to be criminally underrated in this role. Diana Taverner’s scenes at Regent’s Park this season carry a genuine sense of institutional rot, bureaucrats more concerned with optics than with the agents dying under their watch, and Scott Thomas plays every calculation behind her eyes without ever tipping her hand. It’s the kind of performance that wins awards in a fairer universe, though the show’s genre trappings probably keep it from getting the recognition it deserves come nomination season.

The Anti-Bond Spy Show, and Proud of It

It’s worth stepping back for a second to talk about why this show occupies such a specific lane in the spy genre. Everything else in this space, from the big screen Bond pictures to the glossier streaming thrillers chasing that same audience, sells competence as glamour. Slow Horses sells competence as something almost embarrassing, a quality that gets you exiled to a grubby office above a Chinese takeaway rather than a corner suite at Vauxhall Cross. Its heroes are drunks, burnouts, and screwups, and the show’s entire comic and dramatic engine runs on watching people who have already failed once try not to fail again, usually while being actively despised by the people who are supposed to be running the operation.

Season six leans into that identity harder than most of the seasons before it. There’s a sequence roughly two-thirds through the run, involving a stakeout that goes wrong in the most mundane possible way, that captures the show’s whole ethos in about four minutes: no gadgets, no elegant escape, just bad luck and worse decision-making compounding into disaster. It’s the kind of scene that would be an afterthought in a bigger, shinier spy show and is instead one of the season’s best. If you’ve ever wondered why this show keeps winning over critics who are otherwise burned out on the genre, that’s the answer sitting right there.

Where the Season Stumbles, Slightly

If there’s a real criticism to make, it’s pacing in the middle stretch. Compressing two novels’ worth of plot into six episodes means a couple of mid-season hours feel more like connective tissue than fully realised chapters in their own right, and one or two supporting threads get less room to land than they deserve. It’s a minor gripe against a season that otherwise moves with real purpose, but it’s noticeable if you’re watching episode to episode rather than binging the whole run once it’s fully out.

The show also leans, as it always has, on a somewhat grey visual palette that some viewers find monotonous by this point. It’s a deliberate choice, all drab offices and rain-slicked London streets standing in stark contrast to the polished, gadget-heavy spy fiction this show is quietly mocking, but six seasons of the same muted colour grading does start to feel like a stylistic tic rather than a statement.

The Verdict

Slow Horses season six doesn’t reinvent what’s made this show great, and it doesn’t need to. What it does is prove, for the sixth time running, that a cast this stacked and writing this sharp can keep finding new angles on the same basic idea: that failure and humiliation, treated honestly, can be funnier and more affecting than the slick heroics of every other spy show on television. A slightly baggy middle stretch keeps it from being a flawless season, but Oldman, Lowden, and a note-perfect Kristin Scott Thomas make this an easy recommendation whether you’ve been here since season one or you’re thinking about jumping on board for the first time.

Frequently Asked Questions

1. Do I need to have watched the previous five seasons of Slow Horses to follow season 6?
It helps significantly, since the season leans on established relationships between characters like River Cartwright, Jackson Lamb, and Diana Taverner. New viewers can follow the central plot, but the emotional weight lands much harder with the earlier seasons under your belt.

2. Which books does season 6 adapt?
Season 6 adapts Mick Herron’s novels Joe Country and Slough House, compressing both into a single six-episode run.

3. Is Olivia Cooke back for the full season?
Yes, Olivia Cooke returns as Sidonie “Sid” Baker and features prominently across the season, with strong chemistry alongside Jack Lowden’s River Cartwright.

4. How many episodes are in Slow Horses season 6, and when do they release?
The season runs six episodes, released weekly on Apple TV+ starting September 16, 2026, with the finale landing October 21.

5. Is season 6 a good jumping-on point for new viewers?
It’s watchable on its own thanks to clear plotting, but the show rewards viewers who’ve followed the Slough House ensemble from the start. New viewers are better served starting from season one if they want the full emotional impact.