Slow Horses Season 4 has been slated for quite some time, and it seems that the series' next installment is coming soon.

Slow Horses was renewed for Season 4 at the same time it was renewed for Slow Horses Season 3, so we're expecting this installment before the year is over.

Fans, prepare yourselves for more of Gary Oldman in his iconic role as Jackson Lamb in this thrilling series as he's joined by a slew of new cast members in Season 4.  

Who is Joining the Slow Horses Season 4 Cast? 

While there is little information known about many upcoming series, there is a lot of information about the upcoming Slow Horses Season 4, including the cast members. 

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Season 4 will see many new faces joining the cast, including Hugo Weaving (The Lord of the Rings), Joanna Scanlan (Notes on a Scandal), James Callis Battlestar Galactica), Ruth Bradley (Guilt), and Tom Brooke (Empire of Light).

Alongside new cast members, we can expect several returning faces to the series. 

Returning actors include Gary Oldman, Jack Lowden, Kristin Scott Thomas, Saskia Reeves, Rosalind Elazar, Christopher Chung, Freddie Fox, Chris Reilly, Samuel West, Sophie Okonedo, Aimee-Ffion Edwards, Kadiff Kirwan, and Jonathan Pryce. 

Directing Season 4 is Adam Randall (I See You), and according to Deadline, the season will "open with a bombing that detonates personal secrets, rocking the already unstable foundations of Slough House." 

Is There a Slow Horses Season 4 Trailer?

Right now, there is no official trailer for Slow Horses Season 4. 

Slow Horses Season 3 and Season 4 were greenlit in mid-2022 before Slow Horses Season 2 even aired. 

Seasons 3 and 4 were shot back to back, but there hasn't been word on an official trailer at this time. 

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Slow Horses Season 4 Release Date

Slow Horses Season 3 debuted at the end of last year, leaving fans wanting more of the thrilling drama series. 

Although there is no official release date yet, we can expect to see Slow Horses Season 4 before the end of the year, assuming it's on a release schedule similar to that of previous seasons. 

Considering the fact that Seasons 3 and 4 were shot back to back, there's no reason to believe that the release of Season 4 would be delayed any further. 

Technically, Slow Horses Season 4 could be released a lot sooner than the end of the year, but it makes sense for Apple to stay on its streaming schedule and keep the series on a yearly release. 

What Do We Know About the Slow Horses Season 4 Plot? 

Slow Horses is based on the novel series Slough House by Mick Herron, and each season seems to be following a book from the series. 

The vague description given of Season 4's opening, the bombing that will detail personal secrets and shake the already unstable foundation of Slough House, seems similar to Herron's novel Spook Street, which further suggests that each season is tackling one novel. 

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In the book, a former spy is slowly starting to lose his mind, causing him to commit a series of deadly crimes and cause a lot of destruction. 

Part of the destruction includes the bombing of a crowded shopping mall, perhaps the central bombing at the beginning of the new season. 

The personal connection to the former spy will likely be a central theme in Season 4 and will rock the members of Slough House as they must come to terms with their own failures. 

Not only will the members of Slough House have to look inward at their own failures and shortcomings, but they'll have to really determine what it means to be an MI5 agent. 

Although we can't say for certain just how close the series will stay true to the book, Season 4 promises to be the most enthralling and captivating season yet. 

Showrunner Will Smith teases Slow Horses Season 4 

In an interview with Decider last year, showrunner Will Smith (not the actor) teased the release date of Season 4, noting, "I genuinely don't know.

"But I can tell you that it won't be later than this time next year. So you won't have to wait longer than a year." 

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In the same interview, Smith teased a few storylines that fans can expect to come in Season 4.

Standish and Lamb won't be at odds for long as the two come back together as friends, and we can expect a potential romance brewing between River and Louisa. 

River Cartwright (Lowden) also has a plotline coming up as he possesses a top-secret file. This happens after River and Louisa (Eleazar) make it out of a dangerous situation alive. 

Jackson Lamb recuses Standish (Reeves), but Sean Donovan (Sope Dirisu) dies in pursuit of the file, which may have damaged the British secret services. 

The file is evidence of some serious wrongdoings, including the fact that they killed one of their own for leaking serious intel. 

Who Dies in Slow Horses Season 4?

We know, based on the end of Season 3, that one of the team members has died, but we don't know who has passed yet.

All we know is that Jackson Lamb (Oldman) says that it's inappropriate to shower when they've lost one of their own.

In the meantime, keep following TV Fanatic for updates about the series as we learn more.

Devin Piel, an entertainment news writer from the Midwest with a passion for true crime and binge-streaming the latest Netflix series, is a staff writer for TV Fanatic. You can follow her on X.