Slow Horses Season 6 Episode 4: J.K. Coe Killed as Sid Baker Mystery Deepens
The fourth episode of Slow Horses Season 6, titled “Lost and Found,” has shifted the Apple TV+ spy thriller into a lethal new gear. Following the October 7 airing, the series confirmed the permanent departure of a core Slough House operative, signaling that the show’s final chapters for the season will carry a higher body count than any previous outing.
J.K. Coe, the stoic and often unsettling member of the team played by Tom Brooke, was killed in a brutal knife fight with a Russian GRU assassin named Jim. The death marks the first loss of a current Slough House resident this season, following the earlier murders of former operatives Struan Loy and Kay White in the season premiere. The escalating violence stems from a Russian military intelligence retaliation plot following a Novichok-related operation in Kazan, Russia—an operation that has personal and professional ties to MI5 leadership.
The hunt for Russian assassins takes the team into dangerous territory.
The Return of Sid Baker and the Kazan Connection
The sudden lethality of Season 6 is intrinsically linked to the shocking return of Sidonie “Sid” Baker. Played by Olivia Cooke, Baker was presumed dead since the show’s first season after being shot in the head. Her reappearance in the second episode of the current season has complicated the landscape for River Cartwright and Catherine Standish, particularly as her identity is central to the GRU’s grievances.
Evidence presented in “Lost and Found” suggests that Diana Taverner used Sid’s identity to order an off-the-books assassination on Russian soil. This “Kazan operation” is the catalyst for the current hunt, with GRU agents Jim and Jane systematically targeting anyone connected to Slough House. Taverner’s position is further compromised by media mogul Damien Cantor, who is using leverage over her to facilitate Russian GRU demands. This moral gray area leaves the “slow horses” without their usual safety net at the Park.
A Unique Narrative Structure
The accelerated pace and high stakes of the current season are the result of a specific creative shift in the show’s production. While previous seasons typically adapted one of Mick Herron’s novels at a time, Season 6 is a “mashup” of two books: Joe Country and Slough House. This condensed storytelling explains the rapid-fire deaths and the return of long-dormant characters from the series’ history.
According to the official episode schedule, the penultimate episode of the season is titled “Sayonara.” Written by Sophie Goodhart and directed by Adam Randall, the episode is set to premiere on Wednesday, October 14, 2026. The title alone suggests that more departures are imminent as the team faces the fallout of Coe’s death and the ongoing threat from Russian GRU agents Jim and Jane.
The Kazan operation has exposed ’s off-the-books maneuvers.
For River Cartwright, the crisis arrives at a period of profound instability. As the team moves toward the finale, the investigation into how Sid Baker survived her Season 1 injuries—and why Taverner specifically chose her identity for the Kazan hit—remains the central mystery that could dismantle MI5 from the inside out.
