‘Slow Horses’ Season 6 Episode 5 Recap and Ending Explained: River’s Sacrifice for Sid

Spy narratives often feature deals that seem logical in theory but are horrific in execution. In ‘Slow Horses’, Diana Taverner has mastered this kind of trade, and this week’s penultimate episode reveals the true cost of her actions. The episode, titled ‘Sayonara’, premiered on Apple TV on Wednesday, October 14.

The story picks up immediately after Sid Baker’s kidnapping, intensifying the tension for nearly every character involved. By the conclusion, Sid is fleeing, River makes a courageous decision, and Lamb is more informed than Diana would prefer. Spoilers ahead for the entire episode and its conclusion.

The episode begins with Sid, portrayed by Olivia Cooke, attempting to escape from her captors, Russian agents Jim and Jane. While in the back of their vehicle, she cleverly uses a novelty license plate fridge magnet from a service station gift shop to attack Jane, causing the car to crash and seemingly killing the assassin. Injured, Sid manages to escape into the woods, but Jim is hot on her trail.

Fortunately, River, played by Jack Lowden, is also nearby, having been tracking them in a borrowed car. Jim attempts to drown Sid in a lake, but River intervenes, and together they manage to overpower Jim, drowning him. For a brief moment, it seems like they have overcome the worst.

However, the danger is far from over. MI5 agents arrive to retrieve them, still acting under Diana’s orders. Instead of taking them to the Park, they are taken to a private airfield and military hangar. Meanwhile, Jane’s body has mysteriously vanished from the wreck, hinting that she may have survived.

River persuades the agents to let him make a phone call, connecting Sid with Diana, played by Kristin Scott Thomas. Diana reveals that she couldn’t afford to spare the agent involved in the Kazan hit but can offer Sid as a trade to Vassily, the head of the GRU, as a consolation.

The episode clarifies Diana’s motives. She sought revenge against Russian agents for a previous attack but lacked the budget for a sanctioned mission. Consequently, she orchestrated an off-the-books operation funded by an external investor, using Sid’s identity for cover.

Afterward, she erased all records of Sid from the Park’s archives, drawing attention to Slough House, Sid’s last known department. Vassily then dispatched Jim and Jane to carry out assassinations based on stolen files from that department. Meanwhile, Damien Cantor, the true source of the initial investment, emerges to exploit the situation, leaving Diana vulnerable to blackmail.

First trailer for ‘SLOW HORSES’ Season 6. Releasing September 16 on Apple TV. https://t.co/lktVB8KP8v

— DiscussingFilm (@DiscussingFilm) August 18, 2026

Lamb, portrayed by Gary Oldman, learns about Kazan from River and confronts Diana. He pieces together the events linking Cantor’s investment to his hiring of Frank Harkness to eliminate loose ends. Diana insists that everything is under control, which is also her response to the oversight committee.

The committee has already uncovered her mission and the breach of protocol, partly due to a media interview she conducted. Diana addresses the Limitations Committee with confidence, but in private with Lamb, her position is significantly weaker. The fact that all of Slough House is currently hiding in her vacation home complicates matters.

The flight to Sofia, Bulgaria, poses a real threat. Bulgaria’s neutral status means the Russians can do as they please with Sid, yet Diana still approves the handover. River refuses to let this happen, leading to a confrontation where he and Sid steal a car and go on the run from MI5.

After a flirtatious farewell, River realizes that the only way to give Sid a fighting chance is to buy her some time. He instructs her to flee and they share a quick kiss. The episode concludes with River driving back toward the agents, allowing himself to be captured.

Meanwhile, the rest of Slough House remains hidden, with Shirley preparing Molotov cocktails just in case. Lamb tasks Roddy Ho with investigating Cantor’s schedule, revealing that the media tycoon frequently visits a children’s ballet class. There, Lamb spots Natasha, the Russian broker involved in what is touted as the largest media distribution deal in Russian history.

Cantor has been invited to a dinner with potential business partners, setting the stage for the finale. Harkness is also still pursuing Reece. With only one episode remaining, River captured, Sid on the run, and Diana’s scheme exposed, the season has much to resolve.

The season finale is set to air on October 21 on Apple TV. Questions linger about Sid’s fate, River’s consequences, and whether Lamb can rectify the situation before more lives are lost. Diana’s downfall seems imminent, but she has survived worse challenges.

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