Six seasons in, Slow Horses continues to deliver some of the most gripping spy drama on television. Based on Mick Herron's novels, the Apple TV+ series follows the disgraced MI5 agents of Slough House, who keep getting dragged into the action whether they like it or not. Season 6 raised the stakes to a whole new level, with assassinations, betrayals, and a cliffhanger that has fans buzzing. As we wait for Season 7's 2027 release, here are the six biggest mysteries the finale left us with.
What Happened to River Cartwright?
The season's final moments leave River Cartwright (Jack Lowden) in a precarious state. After a tense season that saw the unexpected return of Sid Baker (Olivia Cooke), River ends up at his grandfather's house, where he sets up a cozy evening with wine and sweets. But just as he sits down, he collapses, and the screen cuts to black. The question is: what caused it? The books offer a clue. In Joe Country and Slough House, River is exposed to the nerve agent Novichok via a contaminated doorknob. If the show follows that path, River will survive but be sidelined for much of Season 7, which is expected to adapt Bad Actors. That would leave Shirley Dander (Aimee-Ffion Edwards) to step up as the primary field agent alongside Jackson Lamb (Gary Oldman).
Can the Slough House Agents Recover from the Safe House Ambush?
The team was on the defensive all season, starting with the shocking murders of former agents Struan Loy and Kay White. They went into hiding, but the safe house was compromised, leading to the tragic death of Emma Flyte (Ruth Bradley). The psychological toll is immense. In the finale, the group gathers in a church to honor their fallen, with Catherine Standish (Saskia Reeves) declining a drink, showing she's still shaken. But the bond between them is stronger than ever. Season 7 will likely explore how they cope with the trauma. Shirley is more hardened, Roddy Ho (Christopher Chung) has field experience now, and Moira Tregorian (Joanna Scanlan) has been brought into the fold. Yet, the atmosphere in Slough House will be different, even if Lamb pretends it's business as usual.
Does Diana Taverner Ever Face Consequences?
Diana Taverner (Kristin Scott Thomas) has always played dirty, but this season she went too far. She ordered an off-the-books assassination using Sid Baker's identity, then tried to erase Sid's records. When the cover-up started to unravel, she handed Sid over to the Russians to appease them. But Lamb has the upper hand now, and he's not letting her off the hook. Meanwhile, politician Peter Judd (Samuel West) has leverage over her, and she's compromised her position as First Desk. The question is: will she face any real punishment, or will she weasel her way out again? The show has a history of letting her escape consequences, but Season 7 might change that.
What Is the Full Extent of the Russian Conspiracy?
Season 6 introduced a coordinated attack on Slough House agents, orchestrated by Frank Harkness (Hugo Weaving) and Russian assassins. But the finale suggests there's more to it. The Novichok attack on British soil and the subsequent cover-up hint at a larger geopolitical game. With the GRU officer Vassily Rasnokov (Merab Ninidze) involved, the conspiracy could extend far beyond what we've seen. Season 7 might delve deeper into the Russian angle, possibly tying into the book Bad Actors, which deals with a disinformation campaign. The show has always been timely, and this could be its most politically charged season yet.
Will Sid Baker Stay in the Shadows?
Sid's return was a major twist, but she's now in hiding, stationed at David Cartwright's house. She's clearly still a skilled operative, but her future is uncertain. Will she be drawn back into the field, or will she remain a ghost? Her relationship with River is complicated, and his collapse at the end of the season could force her to step out of the shadows. The books don't feature Sid prominently after Slow Horses, but the show has deviated before. Fans are hoping she'll play a bigger role in Season 7, especially if River is out of commission.
What Role Will David Cartwright Play?
David Cartwright (Jonathan Pryce) has been a looming presence, but his role in Season 6 was limited. His house became a safe haven for Sid, and his past actions continue to haunt the present. With River's fate uncertain, David might be forced to take a more active role. The books suggest he has his own secrets, and Season 7 could explore his connection to the larger conspiracy. Could he be the key to unraveling the mystery? Or will his past come back to bite him? Either way, Pryce's performance is always a highlight, and we're eager to see more of him.
As we count down to Season 7's new cast additions, these mysteries are sure to keep fans talking. The show has proven it can surprise us, and with the source material as a guide, the next chapter promises to be just as thrilling. For more on the show's most shocking moments, check out our ranking of its biggest deaths. And if you're a fan of spy dramas, you might also enjoy The Diplomat's Season 5 mysteries.
