Slow Horses Season 6 Resurrects A 'dead' Character – Here's How They Survived

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This article contains spoilers for "Slow Horses" Season 6, Episode 3, "Resurrection."

At the very end of "Slow Horses" Season 6, Episode 2, "Daddy Issues," perpetual screw-up MI5 agent River Cartwright (Jack Lowden) storms into his dead grandfather's house, crowbar in hand, ready to brawl with his mercenary father (Hugo Weaving). But he's stopped in his tracks when he finds someone else in the house instead: Sidonie Baker, played by "House of the Dragon" actor Olivia Cooke.

It initially seemed that Cooke would be a main cast member of this show, but as we explained when we wrote about Sid's apparent fate on "Slow Horses," her character was shot in the head back in Season 1. The last we saw her, she was unconscious in a hospital bed, and a couple of episodes later, MI5's Diana Taverner (Kristin Scott Thomas) tells Slough House head honcho Jackson Lamb (Gary Oldman) that "Sid Baker is gone." At the time, most viewers naturally assumed that meant the character was dead.

But now Sid's back. How, exactly, did she survive getting shot? And where has she been all this time? These questions had already been answered in author Mick Herron's "Slough House" novels, but thanks to Season 6's third episode, "Resurrection," TV watchers have finally learned the truth as well.

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In the world of "Slow Horses," Sid's been completely out of the picture for three years. As she explains to Cartwright here, she survived getting shot, totally unaware that Taverner wiped the young agent's records from existence and implied Sid was dead. (I suspect we'll hear more about that decision from Diana's perspective later this season.) A piece of the bullet is still lodged in her head, and Sid says it occasionally talks to her; humorously, she's named it "Poirot," the name of mystery novelist Agatha Christie's famed detective (who was recently portrayed by Kenneth Branagh in a trilogy of movies).

We also learn that a few weeks before the events of this episode, Sid received a travel order from the Park (Regent's Park Headquarters, MI5's HQ) for the Russian city of Kazan, but the Park claimed it was just a glitch. Days later, two Russian assassins (played by MyAnna Buring and Kyle Soller) showed up at the village where Sid had been rehoused following her recovery stint in the hospital, but Sid managed to escape before they got to her. Eventually, Sid and Cartwright surmise that an MI5 agent likely used Sid's name and murdered a Russian agent in Kazan, inspiring the assassin duo to come after her for revenge.

Meanwhile, Cartwright has spent the last three years thinking he was responsible for Sid's "death." The two have an amusing back-and-forth about Cartwright centering his own trauma above Sid's, but jokes aside, it's easy to see that the guilt and responsibility of that loss has weighed heavily on him since the start of the show.

Can Sid be trusted? We'll find out as "Slow Horses" Season 6 continues on Apple TV, with three more episodes to go.