Olivia Cooke has revealed she told "quite a lot of people" about her character Sid Baker's return in Slow Horses season 6. The Apple TV series, which returns on September 16, unveiled in its trailer that Sid, presumed dead since season 1, is alive and reunites with River Cartwright (Jack Lowden).
How Sid Baker Survived
Sid was seemingly killed off after a gunshot wound to the head in the first season, but it transpired it was a cover-up. She was a sharp MI5 agent assigned to Slough House, and her body was never shown to viewers, though records of her existence were erased.
She had been following far-right journalist Robert Hobden (Paul Hilton) when she was shot by a masked intruder during a surveillance mission. Taken to hospital, MI5 Deputy Director Diana Taverner (Kristin Scott Thomas) claimed she died from her injuries.
Olivia Cooke on Keeping the Secret
Speaking to Elle in August 2026, Cooke said she had always heard "murmurings" about her return but it was never guaranteed. "I didn't know how faithfully they were going to keep to the books, but there were various availability checks over the years," she said. "I was like, 'Okay, they're still hoping to use me at some point'."
She filmed her scenes straight after finishing Prime Video's The Girlfriend at the end of 2024, with all filming truncated to five weeks of night shoots before Christmas. On whether she kept the secret, she admitted: "I've told quite a lot of people. I keep forgetting because people are like, 'Oh, what are you up to?' I'm like, 'Oh, I'm just shooting Slow Horses'. They were like, 'You were shot in the head, you died'. And I'm like, 'Thanks. Thanks for that'. So yeah, technically a secret. I find it very hard to keep secrets about myself."
Slow Horses season 6 premieres on Apple TV on September 16.
