Slow Horses Gets Personal in Season 4, Revealing the Spy Drama’s Beating Heart

Blame it on the end of Peak TV. Consider it an unexpected upshot of last summer’s dual strikes that ultimately meant even fewer shows to watch. Or better yet, call it what it probably is: the success that sometimes comes from being one of television’s best shows. However you want to explain it, Slow Horses has finally broken through in a meaningful way, and for those of us who’ve been championing the Apple TV+ drama since its debut in spring 2022, the recognition it’s received this past year has been immensely gratifying, especially when you consider the number of worthy shows that never get their due.

After three seasons as one of TV’s best and most entertaining dramas, the espionage series based on Mick Herron’s Slough House novels garnered nine Emmy nominations, including a bid for Best Drama Series and acting nods for stars Gary Oldman and Jack Lowden. It’s well deserved, and the fact that Emmy voters saw fit to recognize the series about a disgraced group of MI5 agents in such a complete way—it also nabbed nominations in writing and directing—means we can finally move past the platitudes about how the series is the best show you’re not watching and focus on what makes it so.

The fourth season adapts Spook Street, the fourth novel in Herron’s series about Slough House, the dumping ground of MI5 that is home to the service’s biggest screw-ups. At the center of the story are River Cartwright (Lowden) and his grandfather, David (Jonathan Pryce), who was once a high-ranking member of the intelligence service but is now living with dementia, which causes him to appear increasingly paranoid. When a car bomb goes off in a crowded shopping center, it naturally puts everyone on edge, but things get worse after it’s discovered the perpetrator was using an MI5-created identity. It eventually comes out that David once crossed paths with the group responsible for the attack, and his ability to identify its leader (played by a deliciously evil Hugo Weaving) puts a target on his back and River in the emotional crosshairs as he tries to protect his grandfather. However, because of David’s failing memory and disoriented state, River is largely on his own. Which is to say, it’s only a matter of time before Jackson Lamb’s (Oldman) slow horses find themselves embroiled in yet another operation far beyond their pay grade and with the potential for far-reaching consequences. 

By now, we’ve seen enough to know what to expect from each new season of Slow Horses. In addition to tense standoffs and the occasional action set piece, the spy series never passes up an opportunity to remind us of the corruption that taints MI5, and that’s present yet again as Diana Taverner (Kristin Scott Thomas), the service’s formidable deputy director general, tries to contain the news about the bomber’s fake identity while also trying to prevent future attacks. This time around, some character additions introduce new layers to the proceedings and provide more people for Taverner to dress down and try to manipulate: Claude Whelan (James Callis) takes over for Tearney (Sophie Okonedo) as First Desk, despite being out of his depth, and Emma Flyte (Ruth Bradley) acts as Duffy’s (Chris Reilly) unflappable replacement for the head of MI5’s internal security.

This is not the first time the personal and professional have been entwined, of course, but it is the first time the emotional stakes extend beyond the members of Slough House. Meaning, this isn’t a romance between Louisa (Rosalind Eleazar) and Min (Dustin Demri-Burns). This isn’t the friendship between Shirley (Aimee-Ffion Edwards) and Marcus (Kadiff Kirwan) that provides the series with much of its banter. This isn’t even Lamb rescuing Standish (Saskia Reeves) from her kidnappers. This is about family, secrets, and the lengths one will go to protect both. Now, you can argue family has always been at the heart of the series—David, who raised River, has been circling the outer edges of the story from the start, while Lamb has shown time and again that he shows up for his ragtag band of misfits even as he pretends to care little for them—but there is a beating heart this season that hasn’t always been present.