Slow Horses season 6 finale release now follows Episode 5, which sends River Cartwright and Sid Baker into the penultimate hour with a kiss after they survive a kidnapping, a crash, and Jim’s death. The episode, titled “Sayonara,” turns the season’s Kazan thread into a fallout hour rather than a bridge episode.
River and Sid in Episode 5
Episode 5 gives River Cartwright and Sid Baker the sharpest payoff in Slow Horses Season 6: he runs after the car carrying Sid, Jim, and Jane, then saves her from drowning before they kill Jim. Sid also uses the “River” novelty plate she bought last episode to slash Jane while driving, which makes the escape sequence feel less like a rescue and more like a fight for control.
The car does a few barrel rolls and settles upside down, so the sequence keeps shifting from pursuit to survival without pausing for relief. River then tells Sid about his grandpa’s death, and the two flirt before Sid is meant to take off on a Russian plane to Bulgaria, which gives the episode its briefest clean line of hope.
Diana Taverner and MI5
Diana Taverner gets her own pressure point when MI5’s all-male oversight committee questions her about the details of the Kazan hit. She answers by leaning into the scrutiny and saying she has the situation under control, a move that keeps her in command even as the off-book operation draws attention.
That sequence matters because it keeps the season’s political machinery running while River and Sid are stuck in a far more personal emergency. The review also places much of the hour in foggy countrysides, which suits the episode’s mechanics: movement, concealment, and one bad decision cascading into the next.
Sayonara and the explosion
The complication is that the episode gives River Cartwright and Sid Baker a rare hopeful moment, but the same hour ends with a grand gesture and a huge car explosion. That is the right way to read Slow Horses Season 6 now: the show has given them a payoff, but it has also set the finale up to burn through whatever stability they just found.
So the practical watchpoint is simple. If Episode 5 is the setup, the finale has to answer whether River and Sid’s brief connection survives the blast radius of Jim’s death, the Kazan fallout, and whatever comes after that explosion in Slow Horses Season 6.
