Everything To Know About ‘Slow Horses’ Season 4 On Apple TV+

It’s been less than a year since Slow Horses aired its eventful Season 3 finale on Apple TV+, but fans will be thrilled to learn that we already have so much insight on Season 4. 

The beloved espionage thriller, based on Mick Herron’s Slough House book series, follows the high-stakes adventures of misfit MI5 agents Jackson Lamb (Gary Oldman), River Cartwright (Jack Lowden), Louisa Guy (Rosalind Eleazar), Roddy Ho (Christopher Chung), Shirley Dander (Aimee-Ffion Edwards), Marcus Longridge (Kadiff Kirwan), Catherine Standish (Saskia Reeves). 

Season 3’s six exhilarating, action-packed episodes saw the group trying to rescue one of their own and expose deep corruption within the agency. As Decider noted after the finale, the season ended with a number of compelling character rifts, cliffhangers, and burning questions. So it’s no surprise fans are eager for new episodes to drop.

If you, like Decider, are desperate for Slow Horses Season 4, you’ve come to the right place. Curious when the Apple TV+ series returns with new episodes, wondering if filming is complete, or which Mick Herron novel is being adapted this time around? Perhaps you want to know what Slow Horses Season 4 will be about and what first-look Season 4 images look like? Or maybe you’re hoping to hear Slow Horses teases straight from showrunner Will Smith?

Whatever your wish, we’ve got you covered. Read on to learn everything we know about Slow Horses Season 4 on Apple TV+, including comments from the showrunner himself. 

Will There Be A Slow Horses Season 4 On Apple TV+?

In case you hadn’t heard, Apple TV+ simultaneously renewed Slow Horses for Season 3 and Season 4 back in June 2022, which means we haven’t seen the last of our favorite rogue MI5 agents.

Slow Horses Season 4 Premiere Date: When Does Slow Horses Return With New Episodes On Apple TV+?

So when are we headed back to Slough House? Slow Horses Season 3 aired its finale on December 27, 2023, and when we spoke with showrunner Will Smith, he assured us that “it won’t be later than this time next year… You won’t have to wait longer than a year.”

Turns out, Smith kept his promise! Apple TV+ recently announced that Slow Horses will return with Season 4 on Wednesday, September 4.

How Many Episodes Are In Slow Horses Season 4?

Like Slow Horses seasons past, Season 4 will consist of six episodes. After the first two episodes of Slow Horses Season 4 premiere Wednesday, September 4, the series will follow a one-episode weekly release schedule until its October 2 finale.

Slow Horses Season 3 Ending Explained: What Will Slow Horses Season 4 Be About? Showrunner Will Smith Weighs In

If you’re looking for a detailed recap of the Slow Horses Season 3 finale, Decider’s Ending Explained article has you covered. As for Season 4 storylines, Apple TV+ shared that “Season 4 opens with a bombing that detonates personal secrets, rocking Slough House’s already unstable foundations.”

As noted in a previous article, those who made it to the end of Slow Horses’ Season 3 finale will have seen a teaser for Season 4, which offers glimpses of Lamb, Standish, Louisa, River, Shirley, Marcus, Roddy, and Diana. We see several new characters, as well, with Hugo Weaving, Ruth Bradley, Joanna Scanlan, James Callis, and Tom Booke joining the cast. And the preview also shows agents dealing with the bomb, River running (and later fighting) for his life, his grandpa screaming, and Lamb explaining that one of his team members just DIED (!!!).

When chatting with Decider ahead of Season 3’s finale, Smith also teased some Season 4 storylines. For instance, although Season 3 ended with a Standish/Lamb breakup, Smith says “It’s very hard to imagine Slough House without Catherine. Lamb isn’t going to function well without her. Lamb needs Catherine…If you enjoyed that [gas station] scene, you’re going to enjoy some scenes in the next series.”

He also hinted at a potential exploration of friends-to-lovers with River and Louisa, saying, “We’ve definitely played with that, I would say. And I think that comes from their performance, that comes from that hug as much as anything. And I think people would want to see them together, but all I could say is we’re going to be true to the character dynamics of the books. It’s definitely — the question will not go unanswered. Put it that way. It’ll be in a Slow Horses way. And it will be messy.”

Fans of shared Jack Lowden and Jonathan Pryce scenes have a lot to look forward to in Season 4 as well. “That scene of them in the club is another one of my favorite scenes we’ve ever done… And that inspired me directly to go and write a scene for the end of Series 4,” Smith said. “It goes to a very heartfelt, very, very sad place and we continue to mind that in Spook Street, partly because that’s where the books go. That’s where this story goes. You know, the seeds that we’re sowing there lead directly into the events of Book 4, so there’s more of Jonathan and Jack in the next series and yeah, absolutely they reached new heights every time.”

Which Mick Herron Book Does Slow Horses Season 4 Adapt?

Hooked on those teasers and want to know more? You can prep for Slow Horses Season 4 ahead of its release by reading Book 4 in Mick Herron’s series, titled Spook Street, on which the new season will be based.

Per Herron’s website, the Spook Street plot summary is as follows:

What happens when an old spook loses his mind? Does someone take care of the senile spy for good? These are the paranoid concerns of David Cartwright, a Cold War–era operative and one-time head of MI5 who is sliding into dementia, and questions his grandson, River, must answer now that the spy who raised him has started to forget to wear pants. But River, himself an agent at Slough House, has other things to worry about. A bomb has detonated in the middle of a busy shopping center, killing forty innocent civilians—and that may only be the beginning of an escalating security situation.

Slow Horses Season 4 First-Look Images and Footage:

In addition to the teaser at the end of Season 3, you can get a quick glimpse of Season 4 footage in Apple’s WWDC “Coming To Apple TV+” ad and study the eight first-look images below, featuring Jack Lowden, Gary Oldman, Aimee-Ffion Edwards, Christopher Chung, Tom Brooke, Kadiff Kirwan, Rosalind Eleazar, Leroy Kincaide, Ruth Bradley, Hugo Weaving, Joanna Scanlan, Jonathan Pryce, James Callis, and Kristin Scott Thomas.

SEASON 4, EPISODE 1

SEASON 4, EPISODE 2

SEASON 4, EPISODE 3

SEASON 4, EPISODE 4

SEASON 4, EPISODE 5

Will There Be A Slow Horses Season 5?

Great news, Slough House stans! In January, Apple TV+ gave Slow Horses an early Season 5 renewal, announcing that the fifth season will be adapted from Herron’s fifth novel, London Rules.

Per a press release, “In season five of Slow Horses, everyone is suspicious when resident tech nerd Roddy Ho has a glamorous new girlfriend, but when a series of increasingly bizarre events occur across the city, it falls to the Slow Horses to work out how everything is connected. After all, Lamb knows that in the world of espionage, ‘London Rules’ should always apply.”

Will There Be A Slow Horses 6 and Beyond? How Many Books Are in Mick Heron’s “Slough House” Series?

Heron has written standalone novels, short story collections, and several novellas throughout his career, but there are currently eight full novels in his “Slough House” series, listed in order of publication here:

• Book 1: Slow Horses (2010)
• Book 2: Dead Lions (2013)
• Book 3: Real Tigers (2016)
• Book 4: Spook Street (2017)
• Book 5: London Rules (2018)
• Book 6: Joe Country (2019)
• Book 7: Slough House (2021)
• Book 8: Bad Actors (2022)

With so much source material in the “Slough House” series, fans are likely wondering if the series will continue beyond Season 4. Though Apple TV+ has yet to officially renew the series for future seasons, Smith says he’d be open to making “really as many as Apple and Gary and the audience want.”

“My only kind of personal feeling on that is that I would always want the last season to be the best. I think every season has to be better. You know, I wouldn’t want the last season to be the last season because people felt that it was past its prime or peaked and now there was nothing more to do. You really want to sort of go out on top. And that’s the challenge — is not to repeat, and to feel it moving on, which the books do,” Smith continued. “…The characters, the ones who aren’t killed off, kind of wear the scars of what happened in the previous books and previous seasons. They’re building. They’re developing. You’re tracking Louisa’s grief in losing Min and how she’s processing that. You’re seeing how Catherine is dealing with everything that she’s been through in the past. So there’s always new things to be doing.”

Stay tuned for more updates on Slow Horses Season 4 (and beyond). Until then, be sure to read Decider’s full interview with showrunner Will Smith and stream Slow Horses Season 3 on Apple TV+.