Olivia Cooke on Returning to ‘Slow Horses,’ On-Set Injuries and That Shocking Finale Cliffhanger: ‘I Want a Showdown!’

SPOILER ALERT: The following article contains plot details from “Judgement Day,” the Season 6 finale of “Slow Horses,” now streaming on Apple TV. “Hello, River.” Those two fateful words announced Olivia Cooke’s return to “Slow Horses” after a four-season absence from the Apple TV spy drama. Cooke’s MI5 agent Sidonie Baker made a brief but […] Olivia Cooke discusses her return to 'Slow Horses' as Sid Baker, working with Jack Lowden and the Season 6 finale cliffhanger SPOILER ALERT: The following article contains plot details from “Judgement Day,” the Season 6 finale of “Slow Horses,” now streaming on Apple TV. Those two fateful words announced Olivia Cooke’s return to “Slow Horses” after a four-season absence from the Apple TV spy drama.

Cooke’s MI5 agent Sidonie Baker made a brief but memorable appearance in Season 1, forging a flirty chemistry with inept spy River Cartwright (Jack Lowden) before dying from a gunshot wound to the head — or so River thinks. Sid’s resurrection wasn’t a total surprise to “Slow Horses” fans: the character comes back in author Mick Herron’s namesake novels, and Apple made little secret of her storyline in the advance promotion for Season 6, which concluded this week. But enough has changed since