Slow Horses Season 6 Confirms Major Return as Olivia Cooke’s Sid Baker Is Back After Shock Fate

Fans of Slow Horses have finally received the news they have been waiting for: Olivia Cooke is officially returning as Sid Baker in the sixth season of Apple TV’s acclaimed spy thriller.

The highly anticipated new season will premiere on Wednesday, September 16, with Gary Oldman returning as the foul-mouthed and unpredictable Jackson Lamb. But it is Cooke’s return that has arguably sparked the biggest excitement, particularly after viewers were left wondering whether her character had survived.

Sid Baker is officially back

© Apple TV

Olivia Cooke will return in the new season

Sid was introduced in the first season as one of the capable MI5 agents working alongside the disgraced spies of Slough House. Her story took a dramatic turn when she was apparently killed after being shot in the head.

However, the series later dropped a major clue that her story might not be over. Roddy Ho discovered that Sid’s official records had mysteriously disappeared, leaving fans to question whether she had somehow survived.

Now, a newly released trailer appears to have provided the answer.

The footage ends with River Cartwright seemingly stunned after seeing Sid standing at the top of a staircase, confirming that Olivia Cooke will reprise the role in season six.

Jackson Lamb faces another deadly threat

The new season promises to put the Slow Horses in an increasingly dangerous position.

Based on Mick Herron’s novels Joe Country and Slough House, season six follows the team as they find themselves on the run after being targeted by two mysterious attackers.

Jackson Lamb is determined to discover why his spies are being hunted down one by one, while Diana Taverner becomes involved in what is described as a high-stakes game of retaliation and revenge.

MyAnna Buring and Kyle Soller are also joining the story as two mysterious figures linked to the attacks.

The new season will also pick up on the fallout from season five, particularly after Diana Taverner’s rise to First Desk, a development that could dramatically alter the balance of power within MI5.

Gary Oldman leads an impressive returning cast

© Courtesy of Apple

Gary Oldman reprises his role as Jackson Lamb in Slow Horses season 6

Alongside Gary Oldman, season six will see the return of 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.

BAFTA winner Lenny Rush is also joining the cast, while Cooke’s return as Sid adds another intriguing layer to the increasingly complicated world of the Slow Horses.

With Sid’s survival finally confirmed and the team facing a new wave of deadly threats, season six looks set to deliver another tense chapter for fans of the series.

When is Slow Horses season 6 released?

© Courtesy of Apple

Kristin Scott Thomas plays Diana Taverner

Slow Horses season six premieres on Apple TV on Wednesday, September 16, 2026.

The season will consist of weekly episodes, with the finale arriving on October 21.