Slow Horses continues to deliver television of the highest order in its sixth season, and Sayonara starts to pay off all the work done in the previous episodes payoff. The episodes builds relentlessly from the previous episode’s cliffhanger and refuses to let up, weaving action, revelation, and unexpected tenderness into a cohesive whole.
The episode opens in the immediate aftermath of Sid Baker’s abduction by the Russian assassins Jim and Jane. River Cartwright desperately commandeers a vehicle complete with the owner’s dog in a moment that blends the series’ signature dry humour with genuine urgency. Meanwhile Sid, ever resourceful even when bound and outnumbered, deploys a novelty licence plate magnet acquired from the service station shops as an improvised weapon. She drives the sharp edge into Jane’s neck, sending the car into a violent rollover. Sid crawls free, bloodied but determined, and staggers into the surrounding woods. Jim, believing his partner dead, leaves a blood trail as he follows.
What follows at the lakeside ranks among the series’ most feral confrontations. Jim overpowers Sid and attempts to drown her, holding her under until the struggle seems lost. River arrives in time to intervene, and the ensuing fight is messy, physical, and entirely believable. Knives flash, fists connect, and the muddy bank becomes a place of life or death. Sid recovers enough to strike Jim with a rock, after which she and River together hold the assassin underwater until the threat ends. The death brings relief, particularly as Jim has easily despatched other members of the team. The Dogs, MI5’s internal enforcement unit, arrive shortly afterward and take River and Sid into custody. Yet the destination is not the familiar corridors of the Park. Instead they are transported to a remote airfield and a cavernous hangar, a shift that immediately signals something is amiss.
It is here that the season’s central conspiracy comes to the surface. River pieces together the truth that has hovered just out of reach: Diana Taverner used Sid’s identity for an off the books assassination operation in Kazan, an unofficial strike against Russian interests funded outside official channels. With the Russians demanding retribution and threatening exposure, Taverner has agreed to trade Sid to the GRU as a form of de-escalation. The phone conversation between Sid and Taverner is ice cold and devastating. Taverner does not soften the reality. Sid is expendable, a convenient solution to a problem of Taverner’s own making. The scene underscores the ruthless pragmatism that has always defined the character. Sid absorbs the betrayal with quiet fury, recognising that the institutional machine she once served has decided her life is the price of institutional survival.
On a windswept stretch of open ground the pair share a moment of hard earned honesty before she is handed to the Russian. They acknowledge the feelings that simmered in the first season, the quiet possibility of ordinary connection in a life defined by deception and danger. They flirt awkwardly, Sid speaks of leaving a light on for him. River refuses to accept the arrangement and makes his move. In a scene of improvised attacked with and physical comedy edge but real stakes, he overpowers several of the Dogs, seizes a maintenance truck, and extracts Sid before she can be bundled on the plane. Their flight across the airfield is brisk and inventive. A fuel tank is kicked free and ignites against a pursuing vehicle in a fireball that allows them brief respite. He instructs her to run across the fields while he turns the truck back toward the oncoming vehicles, drawing the chase away and buying her the only chance she has. The kiss that precedes the separation is brief, urgent, and entirely free of sentimentality but has been coming since the characters first met.
Meanwhile, Jackson Lamb continues his own investigation into the larger forces at play. His pursuit of media figure Damien Cantor and the Russian connections surrounding him adds another layer of institutional rot. Lamb’s interactions remain as caustic and observant as ever, the performance grounded in a weary intelligence that sees through every layer of official murkiness. The contrast between Lamb’s grubby, intuitive tradecraft and Taverner’s high level political manoeuvring has always been one of the show’s great strengths, and it is deployed here with particular effectiveness. Other members of the Slough House contingent, sheltering, strategising in the background, building bombs, and planning a defence provide the familiar dysfunctional camaraderie even as the net tightens around them.
Sid’s resilience and dry wit never desert her even at the point of apparent sacrifice. River’s mixture of competence and self doubt reaches a moment of genuine heroism without requiring him to become someone else. Taverner’s decisions are appalling yet fully in keeping with the institutional survivalism she has always practised. The assassins and the Dogs are credible threats. Even the brief presence of the dog in River’s stolen car plays a role, offering a fleeting note of absurd normalcy that the series has always used to humanise its bleakest corners.
At the end of the episode, Sid is free for the moment yet hunted. River is in custody and facing whatever consequences Taverner and the system choose to impose. Jane’s body has vanished from the crash site, leaving an open question that hangs over the final episode of the season. The larger game involving Cantor, the GRU, and the compromised operations of British intelligence remains unresolved, but the personal costs have become painfully clear. Sayonara earns its title through farewells both literal and figurative, yet it refuses the easy exit. Instead it leaves its characters and its audience in a state of heightened anticipation, the stakes higher and the loyalties more fractured than before.
The episode has everything that makes the series endure: sharp dialogue that cuts without showboating, action that serves character rather than spectacle, a moral landscape in which competence and decency are rarely aligned with institutional power, and humour in the darkest of places. Performances across the board remain exceptional and the storytelling confident enough to let silence and implication do as much work as any speech. As the penultimate episode of the season, it handles both climax and setup with real skill. It gives satisfaction now, leaves room for more trouble later, and we skill don’t know what the hell Harkness is up to.
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Where to watch Slow Horses – Season 6, Episode 5: Sayonara: