Spoiler Space: Slow Horses finally pulls back the curtain on River Cartwright

Spoiler Space offers thoughts on, and a place to discuss, the plot points we can’t disclose in our official review. Fair warning: This article features spoilers of the fifth episode of Slow Horses’ fourth season.

For a spy drama like Slow Horses, which relies on sly character dynamics and psychological conspiring, indulging in several action sequences might seem unnecessary. Besides, we’ve signed up for the mysteries, the grimy and grumpy Jackson Lamb (Gary Oldman), and the show’s hallmark brand of dry British humor. River Cartwright (Jack Lowden) outrunning other people—or even growling hounds at one point in season four—can’t be that much of a feature in comparison to those draws, right? Wrong. 

Apple TV+’s thriller has some coolly filmed chases up its sleeve every season. The show quite literally opens with River seemingly failing his airport test mission, sending him straight into Slough House’s not-so-hallowed halls. Since then, he’s survived gunfights, punches, and a lot more chases. It’s safe to say that, much to our amusement, Slow Horses loves to distress Lowden’s character. (Hey, at least it finally led to an Emmy nomination for the actor this year.) Despite the trend, it’s still jolting to witness River almost die again in “Grave Danger,” the show’s latest episode. Except, as always, Slow Horses pulls off a neat sleight of hand because the shootout isn’t what it appears to be. 

Let’s back up for a minute, though, to unpack everything that leads to River being kidnapped by a maniacal Patrice (Tom Woznikza). You see, this batch of new episodes finally digs into the Cartwright family history. Someone’s trying to kill River’s grandfather, David (Jonathan Pryce), and it’s got to do with a mystery he was involved in 30 years ago in France. Readers of Mick Herron’s novels are familiar with the game-changing twists, of course. But for newbies, putting these clues together in real time (just like River and Lamb do bit by bit) has made for a terrific watch. 

So what the hell is going on? In “Grave Danger,” David confesses to Jackson and Catherine Standish (Saskia Reeves) that decades ago, he freed his daughter from the clutches of a master killer, Frank Harkness, in exchange for fake identities, one of which was used by the man who bombed Westacres mall in the season-four premiere. An even more jarring piece of the puzzle is that Frank’s goal was to cultivate an assassination squad by reproducing and raising his babies as killing machines. (That is one of the most psychotically evil plans we’ve heard, by the way.) 

Anyway, it looks like Frank (Hugo Weaving) succeeded because, in the present day, he’s traipsing around London trying to nab David and River with the help of a dead-eyed Patrice, who is clearly his son, based on the strict, unhinged, yet very personal way they talk. It’s both scary and effective, painting a cruel picture of how Patrice and others like him were probably brought up on that Les Arbres farm. None of this would normally be a huge deal, and we could slot Frank away as a classic Slow Horses villain alongside Alexander Popov and the Sons of Albion, among others.  

We can’t, however, do that because it’s evident that Frank is also River’s father. He has to be, based on the photographic evidence River found, coupled with David revealing that his daughter didn’t want to leave Frank. Maybe she foolishly thought they were in love. This stunning information helps us look at David and River’s relationship in a new light. It’s also fascinating to imagine that River could’ve been creating terror instead of stopping it if he had been brought up by Frank instead. 

This all hits like a ton of bricks in the last five minutes of “Grave Danger.” In that brief time, another slick action scene puts into perspective the contrast between Frank’s (supposed) sons. River is being transported to the Park by MI5 agent Emma Flyte (Ruth Bradley) before Patrice interrupts. Single-handedly, and smack dab in the middle of London traffic, he takes out two other agents and disarms Emma before pointing his gun at River. To be fair, River can’t do much because he’s handcuffed to the car. All he can muster is some kicks, a swat, and a bravely defiant “Fuck you.” 

River doesn’t need to worry because Patrice only wants to presumably take him to their dad. So he isn’t the big death that season four has promised—at least not yet. Let’s just hope River survives and gives his legs a rest before he confronts Frank in next week’s sure-to-be wild season finale. And be sure to check out The A.V. Club’s breakdown of this season with Oldman himself after that episode drops.