Slow Horses Season 6 Trailer Stuns Fans With Olivia Cooke’s Shocking Return

Apple TV+ has released the first trailer for ‘Slow Horses’ Season 6, and the new footage delivers plenty of tension, action and one major surprise. Gary Oldman returns as the foul-mouthed intelligence officer Jackson Lamb, while his team of MI5 outcasts once again finds itself caught in a dangerous conspiracy.

But the trailer’s biggest reveal involves Olivia Cooke, who returns as Sidonie “Sid” Baker. The MI6 agent disappeared from the series after suffering a gunshot wound in Season 2, and fans assumed she had died. Now, Sid is back and ready to shake up the world of Slough House.

The trailer follows Jackson Lamb as he investigates a deadly threat against his fellow spies. As danger closes in on the members of Slough House, Lamb digs into a mystery that connects directly to the past.

Cooke’s return provides the trailer’s biggest shock. Sid suffered a gunshot wound to the head in Season 2, leaving viewers to believe that her story had ended. However, readers of Mick Herron’s novels already knew that Sid survived.

The television series now brings her back into the story, creating a major mystery around her disappearance and eventual return. Sid’s comeback could also change the balance within the intelligence operation as Lamb and his team confront a threat that could destroy Slough House.

Oldman once again takes charge as Jackson Lamb, the abrasive and unconventional head of Slough House. Lamb oversees a group of disgraced MI5 agents who landed at the department after making career-ending mistakes.

Yet the Slow Horses rarely stay out of trouble for long.

Season after season, the supposedly unwanted agents find themselves at the center of major national-security crises. Season 6 continues that tradition, combining British espionage, high-stakes action and dark comedy.

The returning cast includes Kristin Scott Thomas, Jack Lowden, Saskia Reeves, Christopher Chung, Aimee-Ffion Edwards, Rosalind Eleazar, Joanna Scanlan, Samuel West, Ruth Bradley, Tom Brooke, Jonathan Pryce and Hugo Weaving.

Lenny Rush also joins the cast as a new addition to the ensemble.

Season 6 draws from Herron’s novels ‘Joe Country’ and ‘Slough House’. The new story pushes Lamb and his team into another dangerous situation involving revenge and retaliation.

Apple TV+ says Diana Taverner finds herself caught in a dangerous game driven by vengeance. Her predicament soon pulls the Slow Horses into the conflict and forces them to confront another threat from the intelligence world.

The sixth season will feature six episodes, with Apple TV+ releasing them weekly.

‘Slow Horses’ Season 6 premieres September 16, 2026, on Apple TV+. New episodes will arrive weekly, with the season finale scheduled for October 21, 2026.

With Olivia Cooke returning as Sid Baker, Gary Oldman leading the Slough House team and another dangerous conspiracy threatening MI5, the sixth season looks ready to deliver another unpredictable chapter.

Fans can expect more espionage, sharp British humor, explosive confrontations and the twists that have made Slow Horses one of Apple TV+’s most popular dramas.