‘Slow Horses’ Season 4: Showrunner Will Smith Teases Premiere Date, ‘Spook Street’, And More

After six new exhilarating, action-packed episodes, Apple TV+‘s espionage thriller Slow Horses ended with compelling character rifts, cliffhangers, and burning questions.

Based on the third book in Mick Herron’s beloved series, Slow Horses Season 3 followed misfit MI5 agents Jackson Lamb (Gary Oldman), River Cartwright (Jack Lowden), Louisa Guy (Rosalind Eleazar), Roddy Ho (Christopher Chung), Shirley Dander (Aimee-Ffion Edwards), and Marcus Longridge (Kadiff Kirwan) on a quest to rescue their kidnapped colleague Catherine Standish (Saskia Reeves). Along the way, they encountered intel that could threaten MI5’s reputation, so in true Slow Horses fashion they took the moral high ground, saved the day, and exposed the corruption.

After its sharpest season yet, fans will surely be seeking news about Slow Horses Season 4. Has Apple TV+ renewed the series? What will be the focus of future episodes? And which book will Slow Horses Season 4 adapt?

Here’s everything we know about the future of Slow Horses, including comments from our interview with showrunner Will Smith.

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

Great news, Slough House stans! 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. If you make it to the end of Slow Horses‘ Season 3 finale, you’ll even see a teaser for Season 4. Unfortunately, that teaser doesn’t include a premiere date…

When Is Slow Horses Season 4 Coming To Apple TV+? Slow Horses Season 4 Premiere Date:

Curious when Slow Horses Season 4 is coming to Apple TV+? Ahead of the Season 3 finale, Apple TV+ had yet to announce a Season 4 premiere date. But showrunner Will Smith shed some light on when fans can expect new episodes.

“I genuinely don’t know. But I can tell you that it won’t be later than this time next year,” Smith told Decider in a Zoom interview. “So you won’t have to wait longer than a year.”

As a reminder, Season 1 premiered on April 1, 2022. Season 2 started on December 2, 2022. And Season 3 kicked off on November 29, 2023. Judging by past release dates, there’s a chance we could see Slow Horses return in the spring, but our guess is the series will stick with a fall/early winter premiere date in 2024. At least we know we’ll have more Slough House shenanigans before 2025!

Which Mick Herron Book Does Slow Horses Season 4 Adapt?

Want to prep for Slow Horses Season 4 ahead of its release? You can get an idea of where the story is headed by reading Book 4 in Mick Herron’s series, titled Spook Street.

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.

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

In the Season 4 teaser, we catch glimpses of Lamb, Standish, Louisa, River, Shirley, Marcus, Roddy, and Diana, which means the gang will be so back. But we also see several new characters, with Hugo Weaving, Ruth Bradley, Joanna Scanlan, James Callis, and Tom Booke joining the cast. In the preview, we see 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 (!!!).

Aside from that first look and potential Spook Street spoilers above, Smith also teased some Season 4 storylines for Decider. 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.”

Will There Be A Slow Horses Season 5, 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 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+.