Slow Horses season 6 confirmed, but playing strange game with source material

The Slow Horses just keep chugging along, as Apple has officially announced that Slow Horses season 6 is coming just days after Slow Horses season 4 ended and they teased us with what’s to come in Slow Horses season 5 . But there was more to the announcement than just an official green light. Some plot details teased exciting developments that will change the game up for the characters, but also a major tweak in how the show's been adapting the Mick Herron books its based on.

Here is the quick description of the Slow Horses season 6 plot that Apple teased in its announcement: “Season six sees the Slow Horses on the run as Diana Taverner embroils them all in a fatally high-stakes game of retaliation and revenge.” That’s interesting as it could also foreshadow a messy situation in Slow Horses season 5, but another detail adds to the intrigue. Slow Horses season 6 is being adapted from two of Herron’s books, Joe Country and Slough House , a change in format from the first five seasons.

Each of the Slow Horses seasons to date, and the one upcoming in season 5, have been adapted from a single book in Herron’s Slough House series. Now Emmy-winning creator Will Smith is combining two of Herron’s books into a single season that, like all the others, is going to be six episodes long. Though I haven’t read most of Herron’s Slough House books, I can certainly understand how combining two into one season without an expanded number of episodes could cause some concern.

Also, a bit concerning is what this means for the future of the show. Clearly Apple TV Plus sees it as one of their flagship series (hence the early greenlight on season 6), but this combination of books into a single season could mean we’ll ultimately get less Slow Horses than we thought. Herron, to date, has published eight books in the Slough House series. Joe Country and Slough House are number six and seven, respectively, meaning there is only one more book in the main series. Could that mean we’re only going to get one more season of Slow Horses after season 6?

To be fair, there are other books by Herron that are set in the Slow Horses universe that could be used for additional stories should they so choose. And book eight in the series, Bad Actors , was published in April 2023, after the show premiered, so there could be more books on the way, but we'll see. And what happens if the show catches up or surpasses Herron's writing? Game of Thrones fans may have just had a chill run down their spine.

Focusing on the positive though, aside that more Slow Horses is on the way, the main ensemble — Gary Oldman, Jack Lowden, Kristin Scott Thomas, Saskia Reeves, Rosalind Eleazar, Christopher Chung , Aimee-Ffion Edwards, Ruth Bradley , Joana Scanlan and Jonathan Pryce — are all mentioned in the announcement, meaning there’s a good chance they’ll all be part of season 6 (unless its a misdirection so we’re not spoiled on season 5). Also, Samuel West , who did not appear in season 4, is listed, revealing that his character, Peter Judd, will be back.

Slow Horses season 5 does not have a release date yet, but if it follows the timeline for each season it won’t come out until the second half of 2025. Slow Horses season 6 then is likely not arriving until 2026. So whether or not this bit of news is any kind of signal about Slow Horses winding down (we hope not), we still have multiple years left to enjoy the series.

All episodes of Slow Horses are available to stream exclusively on Apple TV Plus .