Slow Horses is one of Apple TV+‘s longest-running and most awarded shows. Gary Oldman plays Jackson Lamb, the brilliant and repellent boss of Slough House, the dead-end MI5 department where disgraced spies are sent to rot. The show adapts Mick Herron’s Slough House novels roughly one per season and has run five so far, with a sixth arriving September 16, 2026. It was one of the picks in our roundup of 11 TV Shows Based on Books, and here is the full series in order, the case each one follows, and which season it became.
The Books in Order
Nine novels so far, read in publication order. The first five line up with the show’s first five seasons. Season 6, premiering September 16, 2026, is the first to combine two books, Joe Country and Slough House, into one story, and Season 7 will adapt Bad Actors. There are also a few standalone novellas set in the same world if you want extra.
Slow Horses
The book that introduces Slough House, the dead-end department where MI5 parks the agents it cannot fire, and the crew of burnouts stuck there under Jackson Lamb. River Cartwright, exiled after a training exercise goes badly wrong, is doing pointless make-work when a young man is kidnapped on camera by a group threatening to behead him on a livestream. What looks like a far-right terror plot pulls the slow horses off the sidelines and into something with far more going on beneath it, and the case keeps shifting under them as Lamb’s people turn out to be sharper than their reputations. Season 1 of the show is built on it.
Dead Lions
An old Cold War spy is found dead on a bus outside Oxford, written off as natural causes until Jackson Lamb, who knew him, decides otherwise. The thread leads back to a network of Russian sleeper agents, the “cicadas,” planted in Britain decades ago and long thought dormant. While River is sent into the field to chase a ghost from the past, Lamb works the case from his own buried history in the service, and the two strands close in on a long-dormant operation waking back up. The show’s second season follows it.
Real Tigers
Catherine Standish, Lamb’s quietly capable assistant, is snatched off the street, and the kidnapping turns out to be leverage. Her captors use her to force River into breaking into MI5 headquarters and stealing secret files, while a power struggle at the top of the service, with the ambitious politician Peter Judd pulling strings, threatens to swallow Slough House whole. The slow horses, more loyal to each other than to anyone above them, break every rule to get one of their own back. The show’s third season is drawn from it.
Spook Street
River’s grandfather, the retired spymaster David Cartwright, once one of the most powerful men in the service, is slipping into dementia, and the secrets locked in his failing memory make him a danger to himself and everyone around him. When a bombing in a London shopping center sends River chasing a lead that runs back toward his grandfather’s past, he finds the old man’s history harder to leave alone than anyone wanted. Season 4 adapts this book.
London Rules
A string of seemingly random attacks across the country turns out to be following a playbook, an old MI5 contingency plan for destabilizing a nation, now being run against Britain itself. As the slow horses work out who is holding the script, a populist MP and a scandal-prone government drift into the frame, and the satire sharpens. Roddy Ho, the team’s insufferable hacker, gets pushed to the front this time, with someone targeting him directly and the rest of the team reluctantly closing ranks around him. The show’s fifth season takes its story from here.
Joe Country
“Joe country” is field slang for hostile territory, and the team ends up deep in it when a connection to a dead colleague pulls them into the snow-covered Welsh hills in the dead of winter. What starts as a search turns into a fight for survival against an enemy who knows the ground better than they do, the cold and the terrain as much a threat as the guns. Season 6, premiering September 16, 2026, adapts this book together with the next one, Slough House, blended into a single story.
Slough House
In a paranoid, post-Brexit Britain, Slough House is being quietly deleted: its budget cut, its name scrubbed from the records, as if the department and everyone in it never existed. At the same time, a new threat surfaces that puts the slow horses squarely in someone’s sights. Lady Di Taverner’s secret funding deal with a corrupt politician has come back to bite, and the team has to fight just to stay alive and on the books. Season 6 adapts this book alongside Joe Country.
Bad Actors
A government superforecaster, part of a think tank advising Downing Street, has gone missing, and a slippery prime ministerial adviser is clearly steering events from the shadows. Underneath it runs a thread of Russian disinformation and a sleeper agent buried inside the British establishment, with Lamb and his crew pulling at threads everyone above them would rather leave alone. Spin, leaks, and the people who manufacture reality for a living all come into play as the team works out who is really running the operation. Set to be adapted as Season 7, expected in 2027.
Clown Town
The newest novel in the series, following Bad Actors. River digs into his late grandfather’s library and a single book that has gone mysteriously missing, a thread that leads back into a Troubles-era cover-up the service would rather stayed buried. Diana Taverner, never one to waste leverage, sets about turning that old secret into blackmail. The slow horses are caught in the middle as the past and present collide again, in a story that ties the long-running threads of the series tighter. It has not been adapted yet, sitting two seasons ahead of where the show currently is.
New to Audible? The Prime Day trial is the cheap way to start the series on audio. Prime members new to Audible get three months free, with a new audiobook each month; without Prime it is usually three months at $0.99 each. Either way you keep what you redeem and can cancel in a click.
Want more like this? See the rest of our 11 TV Shows Based on Books you can read or listen to.
