Everything Slow Horses does is intentional. The Apple TV+ series about the outcasts of British intelligence is almost too taut, structured so compactly around explosions and enemy pursuits and intramural kneecappings that it practically thrums. Amid a TV landscape of saggy dramas and comedies that seem stuck in an existential k-hole, this is the rare show that moves. Which also means that when the fourth season begins with a visual of trussed-up chickens rotating on a spit—identikit bodies raised for slaughter—you can trust that it means something.
Since its debut, in April 2022, Slow Horses—based on Mick Herron’s novels—has preoccupied itself with the theme of failure, and what it allows. The characters are burnouts and duds who’ve either messed up catastrophically at MI5 or offended the wrong person, and have ended up exiled to Slough House, a dank office far from headquarters where leaks and rats aren’t spycraft terms but very real concerns. Nicknamed the “slow horses,” and presided over by the grubby, flatulent Jackson Lamb (played by Gary Oldman), the Slough House spies consistently screw up, even when they succeed. Over the past three seasons, they’ve thwarted white-nationalist terrorists, Russian sleeper cells, heavily armed private militias, even their own MI5 counterparts. But they’ve also failed, sometimes devastatingly, to protect one another. Hovering over them at all times is the possibility of getting called back to MI5 proper, though Lamb’s spies lack the political acumen and the checkered morals to ever actually pull it off.
[Read: The subversive worldview of Slow Horses]
Power is a bleak force in this world, and it’s never been a bleaker one than in the fourth season, a propulsive, nervy trip into the nature of authority, heritage, and care. In its early scenes, a bomb goes off at a shopping center—a terrorist act with minimal leads that sends MI5 scrambling and sets its leaders on edge. The glacial, ruthless Diana Taverner (Kristin Scott Thomas) has been nudged aside as acting First Desk by the smarmy Claude Whelan (James Callis). At Slough House, River Cartwright (Jack Lowden) is worried about his grandfather David (Jonathan Pryce), a former senior official of MI5 whose dementia seems to be getting worse. The slow horses also have two new colleagues: Moira Tregorian (Joanna Scanlan), a cheerful schoolmarm-type who makes the fatal mistake of cleaning Lamb’s office, and J. K. Coe (Tom Brooke), a hoodie-wearing shadow who drums his fingers incessantly but doesn’t say a word. As the centers of gravity shift and realign, the potential for ruthlessness and betrayal seems higher than ever, especially as old secrets surface.
To Taverner’s chagrin, an enterprising associate at MI5 manages to tie the shopping-center attack to one of the intelligence service’s “cold bodies,” or personas that MI5 creates in case agents require new identities. Meanwhile, someone seems to be targeting David Cartwright, whose unraveling sense of reality is hard to detach from his paranoid feeling that he’s being followed. Cartwright’s nickname among spies and even his own grandson is “O.B.,” or “Old Bastard,” and his prominence in Season 4 signals the extent to which the show is thinking about legacy, particularly when a new character (Hugo Weaving) emerges as his inversion. MI5, on the show, is a place where the fish rots from the head down—where diligent agents are burned, shunted out, and scapegoated by grasping, egotistical snakes. How, the series wonders, did it get that way? When and why did the mission change from protecting others to covering your own back?
Whelan, an unctuous suit who’s never worked in the field and whose winning pitch for leading MI5 involved a “triple-A promise” to “activate accountability and accessibility,” immediately passes down the dirty work of getting things done to Taverner. (When the pair meet for a briefing on the top deck of London bus, a prominent ad slyly sells an exhibition dedicated to “Great Leaders: 500 Years of Defining Authority.”) Both contrast delightfully with Lamb, who fails at every aspect of contemporary management by verbally abusing his team, drinking on the job, and making suggestive comments to any woman he encounters. But he also operates according to his own implacable code: protecting agents who are out in the field, refusing to blow their cover, and insisting stubbornly that they’re not bodies to be sacrificed or pawns in someone’s strategic chess game. “Not in front of the kids,” he tells an asset at one point, ever the father figure to these misfit spies.
The characters in Slow Horses, Lamb among them, can sometimes feel like daffy sitcom archetypes that have been air-dropped into a Michael Bay movie. In moments of excruciating tension, when they’re being pursued by trained killers or someone has pulled the pin out of a grenade, they fumble and panic and flail. But they’re also so compelling that I occasionally craved less action and more backstory—fewer knife-edge car chases and more biographical texture. Season 4 delivers on all counts regarding River, who in the past has felt like the show’s normie conduit into the warped world of Slough House, the bland foil to Lamb’s layered grotesque. This season gives River more texture and more to do, allowing Lowden to explore the character’s empathy and demonstrate his sometimes terrifying competence in the field (and his very amateurish French—this being Slow Horses, any display of faculty or skill must immediately be undercut by humiliation).
To its credit, the show manages to do a lot in six episodes: shocking detonations and frantic, drumbeat-scored fight sequences, but also expansive storytelling, detailed worldbuilding, and considered study of what working in intelligence does to people. Some characters (Coe) seem hopelessly traumatized; some (Lamb and the archivist Molly Doran) insulate themselves from damage by shutting everyone out; others (Taverner) have become so cynical that they’ve lost their humanity. The close study of humans, so crucial to espionage, is just as vital to the spy drama. Slow Horses is thrilling, often improbably so. (If this many explosions and gunfights actually occurred in London on a daily basis, the government would have fallen long ago.) But it’s also keenly attuned to the dynamics and psychology of the trade—what it means to understand people as expendable pieces in an unwinnable game.