Apple TV’s Emmy- and BAFTA-winning espionage thriller Slow Horses is gearing up for its return, and Season 6 is set to upend the already twisted rules of the spy game with a major surprise.
As Decider’s full Season 6 review explains, the new installment breaks from the show’s usual format by drawing from two Mick Herron novels: Joe Country and Slough House. The story follows Jackson Lamb, played by Oscar winner Sir Gary Oldman, as well as current and former members of MI5’s misfit Slough House unit. They find themselves pursued by a pair of enigmatic killers, portrayed by Kyle Soller and MyAnna Buring, along with River Cartwright’s estranged father, Frank Harkness, played by Hugo Weaving.
The explosive Slow Horses Season 6 trailer also revealed that a familiar face will step out of the shadows as the team comes under attack: Sidonie “Sid” Baker, played by Olivia Cooke. If her return feels unexpected, there’s a good reason. Neither the Slow Horses nor the audience has seen Sid since the first season. That makes this an ideal moment to revisit Slow Horses Season 1 before Season 6 arrives on Wednesday, September 16.
A return to Slow Horses Season 1 — or simply its first two episodes, where Sid features prominently — offers a useful reminder of Cooke’s sharp performance, Sid’s place within Slough House, and her undeniable spark with River Cartwright, played by Jack Lowden. It also explains why she vanished ahead of Season 2. The first season additionally introduces Samuel West’s far-right politician Peter Judd, another character who returns in a major way for Season 6. For anyone skipping the rewatch, here’s the essential Sidonie Baker recap.
So, what became of Sid Baker in Slow Horses Season 1? Is Sid still alive? What happens to Sidonie Baker in Mick Herron’s books? And what should fans expect from Slow Horses Season 6? Here’s what to know.
Slow Horses Season 1 Recap: What To Remember Before Slow Horses Season 6
During Slow Horses Season 1, River, Sid and their fellow Slough House outcasts are drawn into the desperate effort to save a kidnapped student. Yet the season also begins with River and Sid tailing journalist Robert Hobden, played by Paul Hilton — a routine surveillance job that soon turns dangerous. The premiere made clear that Jackson Lamb placed considerable faith in Sid, while also laying the groundwork for her entertaining connection with River. Their easy, teasing exchanges carried a flirtatious edge and hinted that they could make a formidable duo, professionally and otherwise.
Smart, quick-witted and unafraid to push back against River, Sid consistently kept him guessing. River’s obvious frustration after she left him out of post-work drinks suggested his interest was more than professional. But their promising partnership was about to take a devastating turn.
What Happened To Olivia Cooke’s Sidonie Baker in Slow Horses Season 1?
Early in Episode 2, Sid ignores an incoming call from a contact saved as “Aunt Zadie.” Later, as River sits alone watching Hobden’s home, Sid suddenly climbs into his passenger seat. She tells him she has been tracking him, and the two begin to open up to one another. But when River presses her about the real reason she was assigned to Slough House, Sid refuses to answer — at least until “Aunt Zadie” calls again, twice, and she finally takes the call.
“I can’t talk at the moment. No. I’m watching him right now… I will, but I have to go,” Sid says into the phone. Once the call ends, she admits the person was not her aunt. “There’s a reason why I didn’t tell you why I’m at Slough House… I didn’t just follow you today. That was Taverner, and I wasn’t telling her I was watching Hobden. I was telling her I was watching you… It’s the reason I’ve been sent to Slough House. To keep an eye on you.”
Before Sid can reveal anything further about Diana Taverner’s secret instructions or her true role at Slough House, the pair spot an intruder entering Hobden’s house. They rush to intervene: River heads inside to pull the journalist to safety, while Sid remains outside at the front entrance. River succeeds in getting Hobden out, but as the attacker bursts from the property, a shot rings out. River then discovers that Sid has been struck in the head.
As she was bleeding out on Hobden’s stoop, River called an ambulance, and Lamb revealed in Episode 3 that “she might live.” In Episode 4, River snuck into the hospital and found Sid in a coma in her hospital bed. And in Episode 6, Lamb told a devastated River that she’d passed, assuring him, “I won’t forget Sid. Besides, she was the only good one of you.”
Is Sid Alive In Slow Horses? What Happened To Sidonie Baker In The Slow Horses Books? And Does Sid Return To Slow Horses?
In a massive twist — especially for fans who haven’t read the books — Sid is still alive, as Slow Horses‘ Season 6 trailer confirmed. How? We’ll have to wait and see how things unfold on screen. But we did get a hint she wasn’t dead at the end of Season 1…
After River learned of Sid’s death, Roddy (Christopher Chung) told him he found a lead on their former Slough House colleague. “There’s no record of her ever having been at the hospital. And when I pop through my own private backdoor into MI5’s database, there’s no record of her whatsoever,” Roddy explained. “It means, as far as you know, and even as far as Roddy Ho knows — which is a fuck of a lot farther than anyone has ever known — there is gonna be no funeral, or memorial service, or so much as drinks at the pub for Sidonie Baker. Cause no one named Sidonie Baker ever existed… She might still be alive somewhere.”
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In the books, after Sid was shot and believed to be dead, she returned in Book 7, Slough House, and revealed what happened to her after the life-threatening injury she sustained in Book 1.
What Will Slow Horses Season 6 Be About? Which Book Is Slow Horses Season 6 Based On?
So what else can fans expect from Slow Horses Season 6? As noted, Season 6 adapts Book 6 and Book 7 of Mick Herron’s “Slough House’ series. Here’s what to know:
Joe Country Plot: What Is Book 6 In Mick Herron’s Slough House Series About?
Want more info on Slow Horses Season 6? Here’s the synopsis of Joe Country, straight from Herron’s website:
Meanwhile, in Regent’s Park, Diana Taverner’s tenure as First Desk is running into difficulties. If she’s going to make the Service fit for purpose, she might have to make deals with a familiar old devil.
In Slough House, the London outpost for disgraced MI5 spies, memories are stirring, all of them bad. Catherine Standish is buying booze again, Louisa Guy is raking over the ashes of lost love, and new recruit Lech Wicinski, whose sins make him an outcast even among the slow horses, is determined to discover who destroyed his career, even if he tears his life apart in the process.
Slough House Plot: What Is Book 7 In Mick Herron’s Slough House Series About?
Here’s the synopsis of Slough House, straight from Herron’s website:
At Slough House, Brexit has taken a toll. The slow horses have been pushed further into the cold, Slough House has been erased from official records, and its members are dying in unusual circumstances, at an unusual clip. No wonder Jackson Lamb’s crew is feeling paranoid. But are they actually targets?
With a new populist movement taking hold of London’s streets and the old order ensuring that everything’s for sale to the highest bidder, the world’s a dangerous place for those deemed surplus. Jackson Lamb and the slow horses are in a fight for their lives as they navigate dizzying layers of lies, power, and death.
When Does Slow Horses Return On Apple TV? Slow Horses Season 6 Release Date:
Slow Horses Season 6 premieres Wednesday, September 16 on Apple TV. That said, Apple TV regularly releases new episodes at 9:00 p.m. ET the night before designated premiere dates, so if you’re extra eager to watch, keep your eyes peeled for the Slow Horses Season 6 premiere on Tuesday, September 15 at 9:00 p.m. ET.
Where Can I Watch Slow Horses? Apple TV Streaming Info:
Want to catch up on Slow Horses or rewatch ahead of Season 6’s premiere? Head to Apple TV to stream.
Apple TV comes with a seven-day free trial for new subscribers and has just one ad-free streaming plan available for $14.99/month.
A bundle with Apple TV and Peacock is also available starting at $14.99/month.
Stay tuned for more Slow Horses Season 6 coverage from Decider.