What Happened To Olivia Cooke's Sid In Slow Horses? Her Fate Explained

There's no doubt "Slow Horses" is the best spy show on TV, combining outstanding performances and top-notch action with a sardonic wit to create a wholly unmissable experience. When the series debuted in 2022, it seemed that Olivia Cooke's Sidonie Baker was going to be a major part of that experience, but the character was dispatched fairly quickly after suffering a gunshot to the head. While Sid has yet to return to the series, however, those who've read them will know that she does eventually reappear in the books on which the show is based, which means we may yet see her back on-screen very soon.

There's one thing "Slow Horses" does better than any other spy show: It doesn't dwell on the dearly departed. Much like its often callous protagonist Jackson Lamb (Gary Oldman), the Apple TV series swiftly moves on from bereavement without too much of a fuss. As such, the show embodies not only Lamb's tactical coldness honed over years of spy work (and, as season 5 of "Slow Horses" reveals, abject tragedy) but a kind of stiff-upper-lip British manner — one that is fast becoming obsolete in the age of "The Great British Bake-Off" and a collection of cretins who have rotated through the post of Prime Minister as if it were a hosting job on that very game show.

"Slow Horses" is, of course, based on Mick Herron's "Slough House" book series, which to date includes nine novels and five novellas. Thus far, the TV adaptation has worked its way through Herron's stories in order, with season 5 bringing 2018's "London Rules" to the small screen. The upcoming sixth season is set to adapt both the sixth and seventh novels, "Joe Country" and "Slough House," with the latter containing the shocking return of Sid Baker.

In "Slow Horses" season 1, Sidonie Baker was a member of the Slough House team who seemed out of place at the dumping ground for misfit spies — mainly because she was actually good at her job. The talented sleuth is first seen investigating far right journalist Robert Hobden (Paul Hilton) before she helps uncover a sinister plot by the extremist group the Sons of Albion, who abduct young British-Pakistani student Hassan Ahmed (Antonio Aakeel) and threaten to behead him live on the internet.

In season 1, episode 2, River Cartwright (Jack Lowden) decides to surveil Hobden's home but is surprised when Sid shows up to join him and reveals that she's been asked to tail him and is, in fact, only at Slough House to keep tabs on him in general. Before she can explain further, the pair witness a masked man entering the property and quickly follow, even managing to stop the attacker ... only for him to shoot Sid in the head. In the next episode, River visits Sid in hospital, where she lies unconscious but still alive. Later in the season, though, MI5 Deputy Director-General Diana Taverner (Kristin Scott Thomas) informs Jackson Lamb that Sid passed away, and before the season wraps up, we learn that all information about the late spy has been erased.

The only thing is, we never actually get any confirmation of Sid's death beyond Taverner telling Lamb. The series doesn't show Sid's funeral, and the whole thing seems dubious yet still plausible, given the show's proclivity for quickly moving on from characters dying. Anyone who's read the source material, however, will know that Taverner isn't being honest in this scene, as Sid Baker remains very much alive.

"Slow Horses" showrunner Will Smith departed the series following its fifth season, but the show is set to continue with season 6, which has already been shot. Again, that season will combine the books "Joe Country" and "Slough House," and the latter is where Sid makes her shocking return. "Slough House" is somewhat of a sequel to the series' first novel, "Slow Horses," and focuses heavily on River Cartwright in the wake of him losing his grandfather (which should be a blessing, as "Slow Horses" season 5 made a mistake with its more comedic storyline).

In "Slough House," readers learn that after Sid was shot, she was evacuated to a Secret Service facility in the Lake District, an bucolic area in the North of England known for its many fells and walking trails. In other words, it's a fairly secluded area where Sid was able to stay under the radar as she recuperated. Upon her return, it becomes clear that she's not quite as capable as she once was (as you might expect, given she took a headshot and survived). It's these lingering issues that cause River to question her claims of being pursued by killers.

All of which is to say: Assuming "Slow Horses" continues to faithfully adapt its source material, it looks as though we might see Sid Baker return in the upcoming sixth season. Of course, with Smith's departure and questions surrounding Olivia Cooke's availability, there's no guarantee. So, for now, the character remains dead in the world of the show itself. Still, just as "Slow Horses" has shocked us with its deaths, it might also be about to shock us with this major resurrection.

"Slow Horses" is streaming on Apple TV.