Olivia Cooke returns to Slow Horses as Sid Baker, believed dead since Season 1

Olivia Cooke is back in Apple TV's Slow Horses after a four-season absence, Variety reported on 21 October 2026. She plays MI5 agent Sidonie "Sid" Baker, believed dead after a gunshot wound to the head in Season 1. Sid is alive in Season 6, and Apple promoted the storyline ahead of the season.