Slow Horses Season 6 Trailer Arrives: Olivia Cooke Returns as Sid Baker After Five-Year Absence
Apple TV+ has released the Season 6 trailer for its spy thriller Slow Horses, and the biggest surprise is a face fans have not seen since the show's first season. Olivia Cooke returns as Sid Baker, the MI5 agent who vanished after the Season 1 finale, greeting River Cartwright at the top of a flight of stairs in the new footage Deadline, 2026-08-18.
The trailer sets Jackson Lamb's team on the run, caught in what Deadline describes as Diana Taverner's game of retaliation and revenge. Gary Oldman is back as Lamb, the foul-tempered boss of Slough House — MI5's dumping ground for agents who have blown their careers. Kristin Scott Thomas returns as Taverner, the powerful intelligence official pulling strings from above. Jack Lowden is back as River Cartwright, and Christopher Chang as Roddy Ho Deadline, 2026-08-18.
Season 6 runs six episodes and adapts two of Mick Herron's novels: Joe Country and Slough House. Gaby Chiappe adapted the season, with Adam Randall directing. The series is produced for Apple TV+ by See-Saw Films Deadline, 2026-08-18.
The new season premieres on Wednesday, September 16, 2026, with the first episode dropping that day and subsequent episodes following on a weekly schedule. Apple confirmed the date in June 2026 alongside a first-look image Apple TV Press, 2026-06-11; Deadline corroborated it the same day Deadline, 2026-06-11.
The show has built real momentum. Season 5 earned nine Primetime Emmy nominations Deadline, 2026-08-18. The series premiered globally on Apple TV+ on April 1, 2022 Apple TV Press, 2022-03-02, and Apple has kept it on a steady annual cadence — the Season 5 trailer arrived in September 2025 Apple TV Press, 2025-09-03.
For fans of the show, Sid Baker's return is the headline. The character was last seen at the end of Season 1, and her disappearance has been an open thread for four seasons. The trailer does not explain where she has been — it simply shows her standing there, and River's face doing the rest of the work.
What lands beyond the cameo is the sense that Slough House is cornered. Lamb's misfit agents are not cleaning up someone else's mess this time. They are the mess.
