Where to stream Slow Horses season 4 in the UK

Slow Horses season 4 is on its way to Apple TV+.

The popular espionage drama stars screen chameleon Gary Oldman as Jackson Lamb, the boss of a specialist office where MI5’s worst recruits are sent to while away their days. Inevitably though, each of them end up getting pulled back into the game, whether they like it or not.

The show is based on the Slough House novel series by author Mick Herron and has received chunks of critical praise since its 2022 debut, including Emmy wins and a Bafta nomination for Oldman.

Now, a fourth series is on the way — with a fifth already reported to be in the works.

However, before we get too ahead of ourselves, here’s what we can expect from Slow Horses season 4 including its release date, trailers, plot information and more.

How can I watch Slow Horses season 4?

Slow Horses season 4 will debut globally on Wednesday, 4 September on Apple TV+.

The series will consist of six episodes which will be released every Wednesday, taking viewers all the way up to 9 October.

Season 4 is based on Herron’s fourth novel Spook Street, while the show’s recently confirmed fifth series will be based on his fifth spy novel London Rules.

Is there a trailer for Slow Horses season 4?

The threat levels are critical in the first trailer for Slow Horses season 4, during which we see Lamb and his group of spy rejects pulled into an explosive new case.

Volleying city-centre blasts and gags, the short trailer also gives us a little look at the mystery at the centre of the series — one that’ll have a deadly impact on Lamb’s team.

What will happen in Slow Horses season 4?

Slow Horses is based on Herring’s series of spy novels which are set in Slough House, a place where former MI5 agents are sent after they make one too many mistakes. Lamb is the group’s misanthropic boss who comes complete with a dry wit and more than a few skeletons hiding in the closet.

The show’s first outing was based on Herring’s first book Slow Horses, while season two was an adaptation of book two Dead Lions and season three took its cues from the third book in the series Real Lions.

Slow Lions season 4 will be based on book five, Spook Street, and will see its characters impacted by the events of the previous series. New episodes will have a particular focus on Slough House newbie River Cartwright and his grandfather David’s involvement in the intelligence service.

“Retired from the intelligence service, David Cartwright still knows where the skeletons are hidden. But when he forgets that secrets are supposed to stay buried, there's suddenly a target on his back… Jackson Lamb worked with David back in the day,” says the synopsis for the book upon which the show is based.

“He knows better than most that this is no innocent old man. So when River's panic button raises the alarm at Intelligence Service HQ, Lamb will do whatever he thinks necessary to protect an agent in peril.”

The fallout from some documents River leaked at the end of season three will also be explored. His grandfather clearly didn't want that information out in the world — but why?

“The main thing is the fracture that occurs when River is going against his grandfather for the first time, and that’s a big thing for him, and seeing his grandfather in a new light, and he is starting to make his own judgements and not just toe the line. The next series is sad with what happens between River and David,” showrunner Will Smith told the Radio Times.

Elsewhere, someone’s been setting off bombs in London, with the Slow Horses team forced to investigate.

Who is in the Slow Horses season 4 cast?

Oldman returns as Lamb, the sly boss of Slough House and the Slow Horses team. He’s once again joined by Dunkirk star Jack Lowden as River, and Kristen Scott-Thomas as MI5 deputy director General Diana Taverner.

The Slough House team also returns, including Saskia Reeves as Catherine Standish, Rosalind Eleazar as Louisa Guy, Christopher Chung as Roddy Ho, Aimee-Ffion Edwards as Shirley Dander and Kadiff Kirwan as Marcus Longridge.

Game of Thrones star Jonathan Pryce will be back as River's grandfather David, with newcomers including The Matrix baddie Hugo Weaving, Joanna Scanlan, Ruth Bradley, Tom Brooke and James Calls.

Slow Horses season 4 will begin on Apple TV+ on Wednesday, 4 September.