Back to Slough House: Everything You Need to Know Before Slow Horses Returns for Season 6 as the new Trailer drops
With Season 6 of Slow Horses arriving on Apple TV on September 16, 2026, Jackson Lamb’s ragtag team of MI5 rejects is heading back into action. We look back on everything that's happened so far.
The Slough House Playbook: How We Got Here
With Season 6 of Slow Horsesarriving on Apple TV on Wednesday, September 16, 2026, Jackson Lamb’s ragtag team of MI5 rejects is officially heading back into action.
Adapting Mick Herron’s acclaimed novels Joe Country and Slough House, the upcoming six-episode season promises to be the show’s most chaotic yet: the Slow Horses find themselves stripped from official records, completely disavowed by Regent’s Park, and forced on the run across the UK.
Before the new season kicks off, here is your refresher on how MI5’s resident "rejects" have survived—barely—across five seasons of treason, cover-ups, and flatulence.
This article contains spoilers...
Slow Horses season-by-Season Recap
Season 1: The Right to Fail
We are introduced to River Cartwright (Jack Lowden), a promising young MI5 agent banished to Slough House after a catastrophic training exercise orchestrated by Diana Taverner (Kristin Scott Thomas). Slough House is led by Jackson Lamb (Gary Oldman), a brilliant, flatulent Cold War veteran who treats his subordinates with utter contempt. When a far-right group kidnaps a young British-Pakistani student, the "Slow Horses" uncover a dirty MI5 false-flag operation gone completely wrong, saving the hostage and establishing their knack for cleaning up the Park’s messes.
Season 2: Cold War Ghosts
The sudden death of an old Cold War-era agent triggers Lamb’s suspicion, leading to the discovery of a dormant Russian "sleeper" cell active in London. As the team uncovers a plot to detonate a bomb in the city, tragic reality strikes Slough House: agent Min Harper is murdered by Russian operatives, leaving Luisa Guy (Rosalind Eleazar) heartbroken and hardened.
Season 3: Real Tigers
Former administrative head Catherine Standish (Saskia Reeves) is kidnapped by "Chieftain," a private security firm hired by MI5 insider threat Alison Dunn before her death. The plot spirals into a deadly breach at an MI5 record facility, exposing how deep political corruption runs within the security services. Standish discovers the truth about her former boss (and Lamb's connection to his death), briefly quitting Slough House in the aftermath.
Season 4: Blood and Family
A suicide bombing at a London shopping center leads straight back to France and the mysterious estate of "Les Arbres." River discovers his grandfather, legendary MI5 figure David Cartwright (Jonathan Pryce), is being targeted by French mercenary Frank Harkness (Hugo Weaving). River learns the horrifying truth that Harkness is his biological father—and that David Cartwright traded firearms and blank IDs to Harkness years ago, inadvertently spawning a squad of raised assassins.
Season 5: "London Rules"
The most recent season puts unbearable tech expert Roddy Ho (Christopher Chung) at the center of a deadly terrorist conspiracy. When a mass shooting shocks a London square, the team investigates why Roddy suddenly has a stunning new girlfriend, Tara (Hiba Bennani). She turns out to be a honeytrap linked to an extremist cell using MI5's own internal missteps to destabilize London.
The season ends on a surprisingly poignant note: Lamb spins a story about an East German Stasi interrogation to give the team an escape plan, only for viewers to learn in the finale that the tragic story—and the physical scars—were Lamb's own.
Watch the Slow Horses Season 6 trailer
<blockquote class="twitter-tweet" data-media-max-width="560"><p lang="en" dir="ltr">Father knows best.<br><br>Catch up on <a href="https://x.com/hashtag/SlowHorses?src=hash&ref_src=twsrc%5Etfw">#SlowHorses</a> before Season 6 premieres September 16. <a href="https://t.co/dUPzYoIgiC">pic.twitter.com/dUPzYoIgiC</a></p>— Apple TV (@AppleTV) <a href="https://x.com/AppleTV/status/2084342349925171270?ref_src=twsrc%5Etfw">August 3, 2026</a></blockquote> <script async src="https://platform.x.com/widgets.js" charset="utf-8"></script>Where Every Character Stands Heading into Season 6
What to Expect in Season 6
Premiere Date: Wednesday, September 16, 2026 (Apple TV+)
Format: 6 episodes, releasing weekly every Wednesday through October 21.
New Cast: BAFTA-winner Lenny Rush joins the ensemble cast.
The Stakes: The team goes on the run across the UK after being erased from official records, turning the hunted into the hunters.
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