Olivia Cooke Is Back! Slow Horses Season 6 Trailer Reveals Sid Baker’s Return

Slough House has plenty of problems heading into Season 6, but Apple TV just gave Slow Horses fans one very good reason to celebrate: Sid Baker is back.

The official Slow Horses Season 6 trailer has arrived ahead of the show’s September return, bringing Gary Oldman’s Jackson Lamb and his wonderfully dysfunctional collection of MI5 agents back for another dangerous mission. This time, however, the Slow Horses are not simply getting dragged into somebody else’s mess. They are the ones being hunted, and the trailer makes it pretty clear that Lamb would prefer everyone listen to him before somebody ends up dead.

Good luck with that. This is Slough House we are talking about.

Season 6 finds Diana Taverner pulling the team into what Apple describes as a deadly game of retaliation and revenge, eventually forcing the Slow Horses to go on the run. The trailer shows Lamb warning his team that they are being targeted, while River Cartwright and the rest of the group find themselves caught in another increasingly dangerous situation that threatens to get very personal.

As if that were not enough to get fans talking, the trailer saves its biggest surprise for Olivia Cooke.

Cooke is officially reprising her role as Sidonie “Sid” Baker, bringing the fan favorite character back into the world of Slow Horses after a very long absence. Sid was shot during the first season, and while questions surrounding what actually happened to her have lingered ever since, viewers have not seen Cooke in the role for years.

The new trailer finally changes that. Sid appears before a stunned River, immediately creating plenty of questions about where she has been, what she has been doing and why she is resurfacing now. Considering Slow Horses rarely brings someone back without making their return considerably more complicated than it initially appears, River probably should not start planning the welcome home party just yet.

Cooke’s return also comes at an interesting time for the actress, who has spent the past several years starring as Alicent Hightower on HBO’s House of the Dragon. Seeing her step back into Sid’s considerably different world should be a treat for viewers who have been waiting for the series to revisit one of its earliest mysteries.

The rest of Slough House is back as well. Oldman returns as Jackson Lamb alongside Jack Lowden as River, Kristin Scott Thomas as Diana Taverner, Saskia Reeves as Catherine Standish, Christopher Chung as Roddy Ho and Aimee-Ffion Edwards as Shirley Dander. Rosalind Eleazar also returns as Louisa Guy, while Hugo Weaving is back as Frank Harkness and Lenny Rush joins the ensemble.

Season 6 draws from Joe Country and Slough House, the sixth and seventh novels in Mick Herron’s book series. Gaby Chiappe adapted the new season for television, with Adam Randall returning to direct.

The trailer suggests the series is sticking with the combination that has worked so well for five seasons: dangerous espionage, people making questionable decisions and Jackson Lamb somehow remaining both the smartest and most unpleasant person in practically every room he enters. Putting the agents themselves in the crosshairs gives Season 6 an especially personal hook, but bringing Sid back might be the development that has longtime viewers talking the most.

After years of wondering whether Sid Baker would ever walk back through the doors of Slow Horses, Apple TV has finally given us the answer. She is alive, she is back, and judging by River’s face when he sees her, there are going to be a whole lot of questions that need answering.

Slow Horses Season 6 premieres Wednesday, September 16 on Apple TV. The six episode season will release one episode weekly through October 21.