Apple TV Just Made Jack Lowden’s ‘Slow Horses’ Return That Much Harder

Editor's note: The below contains spoilers for the Slow Horses Season 6 finale and Mick Herron's book series.

If one thing is clear in the Slow Horses universe, no one is safe. In the Apple TV hit series' sixth season, the agents of Slough House, past and present, are fighting for their lives after they end up on a kill list, with professional assassins methodically hunting them down. Despite some major characters returning — Sid Baker (Olivia Cooke) and Louisa Guy (Rosalind Eleazar) — and other major characters being killed off — J.K. Coe (Tom Brooke) and Emma Flyte (Ruth Bradley) — Season 6 unexpectedly delivered one more twist in its final minutes.

After a wild season, Slow Horses leaves River Cartwright's (Jack Lowden) life hanging in the balance. While his ultimate fate isn’t explicitly revealed, Mick Herron’s book series provides more clues about what happened and where River may be. Lowden's absence from the Season 7 trailer might make him seem like a goner, but the Slow Horses author has already written the blueprint in Bad Actors, the season's source material.

What Happens To River Cartwright in the 'Slow Horses' Season 6 Finale?

In Season 6, Slow Horses moves away from its typical formula, adapting two of Herron's novels, Joe Country and Slough House, rather than relying on just one book. With that in mind, the season's final scene pulls from the latter novel's events. After returning to his grandfather’s (Jonathan Pryce) home, where Sid has been hiding out, River prepares a romantic nightcap for them. In the process, he picks up the crowbar he'd left on the counter earlier in the season, noticing a sticky substance on his fingers that he attempts to wipe off. Moments later, River collapses as a result of a neurotoxin that the assassin Jim (Kyle Soller) left on the crowbar when he and Jane (MyAnna Buring) infiltrated David Cartwright’s home earlier in the season.

In Herron's Slough House, the same event occurs, but in a slightly different way, with River touching the front doorknob of David's home, which has been laced with the nerve agent. Speaking to The Wrap, Season 6 showrunner Gaby Chiappe stated that it was always the plan to follow Herron's lead. “It’s a really interesting thing Mick did. It’s a bit like, ‘You know I’ll kill people. But you think I’ll kill everyone except Lamb and River. Well, what if I do this to River?’ You don’t know if he’s dead or alive." That coy statement may simply be intended to keep fans hungry for next season, since Herron does confirm River's fate in Bad Actors. In that book, River is essentially absent from the plot, hospitalized and recovering from Novichok poisoning, but ultimately recovers and lives to fight another day.

A River-less Season Could Benefit Other 'Slow Horses' Favorites

Sidelining River from Season 7's action might actually be a good move for Slow Horses. Given the show's large ensemble cast, a River-less batch of episodes could give other agents, like Roddy Ho (Christopher Chung) and Shirley Dander (Aimee-Ffion Edwards), more focus. Based on the Season 7 trailer, Shirley becomes central to the story as she struggles with her own vices, with Jackson Lamb (Gary Oldman) seemingly forcing her into support meetings while also still in the field. Roddy, who lost his latest crush in Flyte, attempted to spring into action last season, but her fate might prompt him to believe he could become a real action hero. Even Diana Taverner (Kristin Scott Thomas) seems to be running into the action!

Another possibility for Season 7 is the full-time return of Louisa Guy, which would follow the plot of Bad Actors. The only element that would complicate this storyline is that she's partnered with Lech Wicinski, an exiled analyst who hasn't been introduced in the show yet. The other new agent that joins Slough House in Herron's novel is Ashley Khan, who, according to IMDb, will be played by former Doctor Who companion Varada Sethu. River will return eventually if Slow Horses' source material is anything to go on, but it shouldn’t come as a shock if Lowden is largely absent when the spy thriller returns for Season 7.

Slow Horses is available to stream on Apple TV.