Apple TV+ has dropped a bombshell with the premiere of Slow Horses Season 5 on September 29, 2025, and it’s already a certified sensation. The latest installment of the acclaimed spy thriller, based on Mick Herron’s Slough House novels, has rocketed to a flawless 100% score on Rotten Tomatoes from 20 reviews, surpassing even its stellar predecessors. Gary Oldman’s unhinged Jackson Lamb returns as the chain-smoking, foul-mouthed head of MI5’s misfit department, leading his “slow horses”—disgraced agents exiled to Slough House—through a labyrinth of espionage, betrayal, and bureaucratic absurdity. But it’s the shocking new cast addition that’s sending fans into a frenzy: none other than Benedict Cumberbatch as a cunning double agent with ties to Lamb’s shadowy past.

The season kicks off with Slough House under siege, as a leaked classified file exposes the team’s failures and draws the ire of MI5’s elite. Lamb’s ragtag crew—Jack Lowden’s River Cartwright, a sharp but unlucky operative; Kristin Scott Thomas’s Diana Taverner, the ice-queen deputy director; and Jack Davenport’s droll Min Harper—must navigate a high-stakes conspiracy involving a rogue tech billionaire and a cyber-attack on London’s financial district. Herron’s razor-sharp plotting shines, blending pulse-pounding action with biting satire on the spy world’s incompetence. Oldman’s Lamb is a revelation, his gravelly monologues and deadpan quips (“Spycraft’s 90% waiting and 10% not shitting yourself”) stealing every scene.

Cumberbatch’s surprise casting as Elliot Kane, a charismatic MI6 liaison with a hidden agenda, elevates the drama to new heights. “Bringing Ben on was a game-changer—he’s got that perfect mix of charm and menace,” showrunner Will Smith said. Their Lamb-Kane showdowns crackle with tension, hinting at a decades-old grudge from the Cold War era. Returning favorites like Rosalind Eleazar as the resilient Louisa Guy and Christopher Chung as the tech-savvy Marcus Longridge round out the ensemble, while new faces like Olivia Williams as a ruthless corporate fixer add fresh layers of intrigue.

Critics are unanimous in praise. The Guardian calls it “a masterclass in spy satire, funnier and fiercer than ever,” while Variety hails the 100% score as “well-deserved for its whip-smart script and Oldman’s tour de force.” On X, #SlowHorsesS5 is trending, with fans tweeting, “Cumberbatch vs. Oldman? My brain exploded!” and “Better than The Night Manager—hands down!” The season’s six episodes, directed by James Hawes (The Crown), blend high-octane chases through rainy London alleys with claustrophobic office banter, all underscored by a jazzy, ominous score.

As Slough House races to avert disaster, Season 5 explores themes of obsolescence and redemption in the modern intelligence game. With Apple TV+ renewing the series through Season 6, the future looks bright for Lamb’s losers. Whether you’re a die-hard Herron fan or new to the slow horses, this season is unmissable. Stream it now—before the spoilers gallop ahead. Slow Horses isn’t just a thriller; it’s a slow-burn triumph that’s galloping straight to Emmy gold.