'Slow Horses' Penultimate Season 4 Episode Brings "Grave Danger"

The penultimate episode of any thriller series is always a great place to review the journey thus far. “Grave Danger,” the fifth episode of Slow Horses’ fourth season, mirrors the second-to-last episodes of the past seasons – the final chunks of crucial exposition are handed over, the stakes are dialed up to maximum voltage, and the plot makes an expected shift to suspense and action, leaving little space for mystery or character plotting. This isn’t a critique, more of an observation of how thriller storytelling works on an episodic level – you gotta have a cliffhanger to make people tune in next week! – but it does mean we can reasonably assess some of the elements that have built up to this structural focal point.

We’ll start with the negatives: it’s safe to say that James Callis’ First Desk Claude Whelan isn’t working as a character. True to form, the latest Slow Horses bureaucratic foil is unsubtle and overperformed. Whelan's sharp turn in this episode from a beacon of institutional accountability to a hysterical rant at burying MI5’s “cold body” false identities being used by a Europe-wide death squad is gratingly obvious and unearned. This character exists to be shot down and humiliated from the off, and we are never given the chance to take his pretty reasonable critiques of The Park seriously. It points to a lack of satirical imagination on Slow Horses’ part.

That’s even before the regressive reveal that he pushed Moira to Slough House because she was close to discovering his habit of visiting sex workers, which undermines the show's claim of giving tired spy fiction a modern upgrade – the trope of a nice, smiley public figure having a seedy, tabloid-fodder vice has been bouncing around for about fifty years. We’re a little past such lowbrow material.

Another misstep this season has been closer to home – the secondary tier of agents in Slough House have been given zilch to do all season. All we’ve gotten from Shirley and Marcus is evidence that they’re ten times more annoying when they’ve got no plot responsibilities; we finally get the obvious payoff to Roddy’s claim he has a long-distance girlfriend (quel surprise, he doesn’t); after becoming one of last season’s best characters, poor Louisa is left with babysitting duty for whole episodes at a time. The most significant thing she does in “Grave Danger” is catch up with River’s aloof, callous mother on what happened with her son and father, a conversation that decisively fails the Bechdel Test.

That said, Season 4’s focus on older characters has been most welcome. Still in the battered black cab from “Penny For Your Thoughts,” Jackson and Catherine focus on extracting the last expository details from the elder Cartwright. Why did David sell cold bodies to Harkness? What was his connection to the young woman Chapman smuggled back into England, who then disappeared on him? As it turns out, she’s David and Rose Cartwright’s daughter who left them to live with Harkness’ squad of “deniable assassins.” David then arranged a sale of MI5 cold bodies to get her back, which were then used to carry out extrajudicial hits across the continent. Where she ended up after Chapman lost her will probably be revealed in the season finale.

Chapman may be dead, but there’s another veteran agent in the firing line – archive queen Molly (Naomi Wirthner). Harkness forces his way into her flat at the start of the episode, and it turns out he’s been communicating with her using an MI5 alias, making Molly another unwitting co-conspirator in his murder plot. Hugo Weaving and Wirthner are terrific in their scenes together – Weaving oozes menace with his growling voice and domineering physicality, adding another sterling villain role to his impressive roster; Wirthner and director Adam Randall emphasize Molly’s vulnerability as a disabled person in a hostage situation in a way that undercuts her usual bullish, obstinate attitude.

Harkness wants to track River, who’s been arrested by Flyte at David’s cottage, presumably to use him as leverage to draw David Cartwright out of hiding. As we learned last week, the West Acres bombing was way more high profile than intended, and now the usually shadowy Harkness needs to off anyone and everyone who could click that his secret family-run French death squad, not to mention the false identities that used to be MI5 property, were linked to the attack. He's also got a new hit list, as shown by the handwritten names we spot in the episode’s final moments – five top players, including Claude Whelan. 

Handcuffed to Flyte’s car, River initially holds back on giving the Chief Dog what she wants, but his knowledge of his granddad’s whereabouts is a few episodes out of date. Unlike Whelan, Flyte feels like a worthy addition to the series – she’s assertive and no-bullsh*t but still aware she's being pushed about by her superiors and operating with limited agency. This puts her on the same wavelength as River, who knows he’s pretty much Jackson Lamb’s pet project. Their conversation driving back to London reflects this well – Lowden and Bradley have good chemistry, matching each other’s frustration and fast-acting intelligence.

Flyte gets close to saving River’s life in the action-packed final sequence, as French assassin Patrice (Tom Wozniczka) steals a garbage truck to ambush the MI5 motorcade and kidnap River Cartwright. Adam Randall has directed every episode this season. There’s a marked improvement in how sharply crafted and suspenseful the action sequences have been – they never go on too long, and they deftly and playfully stretch out the tension. As we leave the penultimate episode, all the dogs have been killed, Flyte is left for dead, and River is bundled into Patrice’s car. Harkness’ secret plan may be out in the open, but he has superior willpower and one last element of surprise on his side. It’ll take some classic eleventh-hour hijinks for these screw-ups to stop him from brute forcing his way to victory.

Slow Horses Season 4 continues with weekly episodes streaming on Wednesdays through October 8, 2024, on Apple TV+.