The 'Slow Horses' Season 4 Finale Says "Hello Goodbye"

Season 4's finale, “Hello Goodbye,” would be more aptly titled “The Many Dads of River Cartwright,” as no fewer than three Slow Horses older men are positioned as father figures to River (Jack Lowden) in the Season 4 finale. This paternal trifecta is the key to understanding what works and what doesn’t work about this season's sixth and final episode. It is also, depending on how you look at it, the best illustration of the show's strengths and weaknesses, an illuminating look at the show’s limitations.

After the motorcade ambush, Patrice brings River to a lovely cafe in Granary Square, Kings Cross, where a cool-headed Frank Harkness awaits him. River shares a revelation that we probably should have put together sooner: that he is Frank’s son. His mother is the young woman Chapman rescued from Les Arbres in exchange for MI-5 cold bodies years ago. Lowden and Weaving do fantastic work across the dining table as the growling and smarmy supervillain projects all his patriarchal possessiveness onto a very emotional young man who only now realizes how much of his family's suffering is because of this one man. Both families, really; Yves blew up the shopping mall because he lost control and wanted to lash out against his dad’s insane mercenary program. However, the scene ends with the real reason he brought Jack here: Harkness has lost most of his boys, so he offers River a job. 

It’s the one dramatic misstep in an otherwise intense scene. There’s never a sense from Lowden that River is tempted to join Harkness & Sons – except for the fact that otherwise, Harkness will try to kill him. That said, the best joke in the episode comes when Harkness spots River covertly phoning Louisa (Rosalind Eleazar) under the table, and when he asks who his son dialed, River answers, “Childline.” Threatening to call the well-advertised child social services line is a recognizable gag to almost every British kid who came of age in the 2000s.

Over at HQ, Whelan has lost the plot, ordering a shoot-to-kill order on not just Harkness but his hostage River Cartwright – and neither Taverner nor Emma Flyte can terminate his assassination order. Louisa, Flyte, and a band of Met police officers surround Granary Square as Harkness emerges with a gun pointed at River, but everybody gets confused when the dogs rush in, and River realizes they’ve been ordered to terminate him. It’s hard to tell what’s funnier, River’s reaction to his own team trying to execute him or that Harkness uses the momentary confusion to stuff a live grenade in his son’s hood. River narrowly avoids getting blown apart, but Harkness disappears into the nearby tube station. It feels like a lot of this show boils down to spies chasing and being chased through tube stations, but we’re not complaining.

Back at Slough House, a siege is imminent. Moira leaves a voicemail on a couple of Chapman’s phones saying that David is back in the building. She doesn’t know Chapman was killed a couple of episodes ago, but now Patrice and Jackson Lamb know to converge on the Park’s most embarrassing fortress. Catherine and Moira hole up in Jackson’s office, with David and the cowardly Roddy hiding in his grotty toilet. As the most capable agents in the building, Shirley and Marcus arm themselves, which involves Marcus getting a lucky break on a sports bet so he has the cash to buy back the pawned handgun. (Remember, kids, gambling is good if you do it to wield lethal force.)

Patrice barges into Slough House like a one-man army, and the sequence where he ascends the building, facing fierce resistance from Marcus, Shirley, and a boiling-hot kettle throw from JK Coe, is a pacy, thrilling pressure cooker of an assassin closing in on his elderly target. Jackson makes a surprise arrival that gives Shirley the upper hand over Patrice, but as he freely bleeds while handcuffed to an office radiator, the team realizes Marcus is dead. 

It’s a sad beat, especially for Shirley, who loses her only lifeline, but it would be more tragic if it didn’t feel obligatory. Marcus hasn’t done much recently – his gun pawn was stretched out over multiple episodes – and the season-long focus on River and the older agents made us realize how stale the core Slough House team can feel if they get too stationary. Someone had to go! Also, after talking Shirley out of killing their prisoner, JK Coe does it himself. He seems to have many issues – hopefully, we’ll see more of them next season.

A second climax happens almost concurrently: chasing Harkness through St Pancras, Flyte’s dogs pursue him to the Eurostar train back to France – but River remembers his dad could watch him when he was chased through the station last episode and quickly spots Harkness in his cozy vantage point in a station bar. They share a quiet moment, another somber beat that would feel better if it had been structured better. River’s parentage twist didn’t have the chance to develop or meaningfully affect anyone this season because it wanted to be a last-minute reveal. It means this final payoff, where River resoundingly rejects the father he grew up estranged from, feels unexciting and uncomplicated.

A series of scenes attempt to wrap up our loose ends: Harkness has prepared several blackmail documents describing the dirty work he’s done for British intelligence, but Taverner dismisses the messy fallout by saying it’s Whelan’s problem. Whelan reinstates Moira at the Park when she threatens him with his sex worker scandal, so it looks like both characters will stick around – hopefully long enough to become interesting. River heartlessly dumps his grandfather at a M-I5-approved retirement home, and ultimately leaves David, pleading with him not to abandon him somewhere he doesn’t want to be.

The cold shoulder River gives David is an expression of how David's connection with Harkness was kept a secret and almost got him killed, but forgive us for thinking our hero was going to double back at the last second, check out his grandfather, and move in with him as his caregiver. Instead, we’re left with a cruel and weak closing best for a main character who may in the future regret his decision, but we’ll have to wait another year (eh, knowing Slow Horses, maybe only ten months) to find out.

Didn’t River begin this season worrying that he wasn’t doing enough for David or showing this difficult man enough compassion? After everything he’s been through, he leaves Season 4 with no evident change in character, deserting his flawed and ailing father figure rather than committing to the messy process of caring for one another. In the final scene, River and Jackson sit over some paperwork in a shabby pub, drinking whiskey in pointed symmetry with one another (making Jackson the third and final dad of the episode). Slow Horses wants to gesture at how easy it is for mistreatment and unhealthy behaviors to repeat across different generations. Surely the show should know by now that getting stuck in self-destructive patterns isn't very compelling, it’s a much bolder choice to break out of them.

Seasons 1 through 4 of Slow Horses are streaming in full on Apple TV+. Season 5 is slated to arrive in 2025.