Did River die in Slow Horses? Season 6 writer reveals what really happened in finale twist

*Warning: Major spoilers ahead for the Slow Horses season 6 finale and the Slough House books*

Jackson Lamb has spent most of Slow Horses season 6 trying to stop his agents from being picked off one by one. But the finale, aptly titled ‘Judgment Day’, is an absolute bloodbath.

At the beginning of episode 6, River Cartwright (Jack Lowden) calls Lamb (Gary Oldman) after escaping the Dogs, and breaks the news that Coe (Tom Brooke) has been killed. 

Lamb reminds him of the “Moscow Rules” – as the Apple TV show puts it, “Moscow rules mean watch your back; London rules mean cover your arse”. Essentially, it’s the old-school spy mentality of trusting absolutely no one and assuming you’re always being watched. Given how things are going for Slough House, it’s probably advice worth listening to.

Meanwhile, Lamb has his own mess to sort out. Diana Taverner (Kristin Scott Thomas) is ready to come clean about the botched Russian assassination operation that put Slough House in danger – but Lamb has other ideas. He hatches a plan to pin all the blame on media mogul Damien Cantor (Hugo Speer), handing him over to the Russians and saving his agents in the process.

But the real chaos is unfolding at Taverner’s Suffolk safe house, where the remaining Slow Horses are hiding out. River’s murderous father, Frank Harkness (Hugo Weaving), turns up with his men, leading to a massive shootout that leaves Emma Flyte (Ruth Bradley) dead and Louisa Guy (Rosalind Eleazar) injured.

River almost gets killed by assassin Jane (MyAnna Buring) too, but Frank unexpectedly saves his son’s life by shooting her. The pair then have a rather awkward father-son heart-to-heart, with River ultimately deciding not to kill him.

After everything, the surviving agents gather to remember their fallen colleagues, and it looks like River might actually get a happy ending for once. He heads home to find Sid Baker (Olivia Cooke) waiting for him, and the pair seem ready to pick up where they left off.

Except this is Slow Horses, so obviously things can’t be that simple.

As River prepares for a romantic evening with Sid, he moves a crowbar out of the way – and there’s clearly something odd on it. Moments later, his hand starts shaking, he struggles to breathe and collapses on the floor. And that’s where season 6 leaves us. 

Has Slow Horses really just killed off River Cartwright? 

The showrunner is being coy about the answer to this and the ending of Slow Horses season 6 episode 6 leaves his fate up in the air. But if you’re desperate to know, the short answer is it’s highly likely River is not dead. 

You see, the Apple TV series is based on the Slough House novels by Mick Herron. Although most seasons have focused on one book, season 6 merged books six and seven – Joe Country and Slough House. Meanwhile, the confirmed season 7 will adapt book eight, Bad Actors.

And that’s good news for River, because he does survive in the books.

Of course, this doesn’t automatically mean the show will follow the same path. Slow Horses has already made some pretty significant changes to Herron’s stories, and the cast and crew are being careful not to give a definitive answer. 

When asked the question by TV Insider, season 6 head writer Gaby Chiappe replied, “We don’t know what’s going to happen to him.” But the finale only just dropped, so it’s understandable they wouldn’t want to give the answer straight away. 

And there’s another reason to be optimistic. Speaking to Gold Derby about the deaths of Coe and Emma, Chiappe said the team wouldn’t kill off characters who survive in the books.

“Those deaths are directly from the books. We haven’t killed – and we wouldn’t kill – anyone that doesn’t die in the books,” she told the outlet. 

“Because these two novels were melded together, the deaths happen in a slightly different way, but I think the spirit of them is retained from the book. Emma Flyte dies protecting others, which is very much how it happens in the book. 

“In the book, she’s not shot by Frank Harkness but that felt like the most meaningful death we could give her in our structure. It was also a good thing to give Frank just in case you were getting sentimental about him.

“But it really does matter to us, and it matters to the actors and it clearly matters to the viewers. A number of people who I know well – and also not so well! – have been texting me going, ‘You killed Coe! What were you thinking?’ And I’m like, ‘Well, to be fair, Mick Herron killed him first.’”

So for them to kill off one of the main characters this way when it doesn’t happen in the books would certainly be an unexpected move to put it lightly. 

Slow Horses writer confirms what actually happened to River 

The reason for River’s deteriorating condition is because the crow bar was contaminated with the deadly nerve agent Novichok.

Originally developed in the Soviet Union during the Cold War, Novichok is a group of highly toxic chemical weapons that disrupt the nervous system, potentially causing muscle spasms, paralysis and respiratory failure. 

Exposure can be fatal, although survival is possible with urgent medical treatment. This is something Chiappe confirmed when speaking to TV Insider about River’s fate. 

“We know that Novichok has been named, and we know that it has been used within the episode, and we suspect that that’s what it is,” she explained. “And people survive it, but people also die from it. So we don’t know what’s going to happen.”

In the Slough House book, River is similarly exposed to the nerve agent, but it’s after touching a contaminated doorknob rather than the crowbar we see in the TV series. His fate is also left uncertain at the end of the novel, much like the season 6 finale.

River is revealed to have survived in the subsequent books, although the poisoning has some seriously nasty after effects. 

Chiappe pointed out to Gold Derby that the groundwork for the Novichok poisoning was actually laid out in Slow Horses season 6 episode 2 when Jim and Jane come knocking and River and Sid hide. 

“You see Jim looking around and there’s a little bottle lying on the table. He looks around and sees the crowbar that River brought in with him, and we have to assume that he paints it with what’s in the bottle, which – given that there have been nerve agent attacks elsewhere – it’s a Novichok attack,” she said. 

“We had a lot of debate about that. Will people know what it is and what’s happening? It’s taken from the book, but in the book it’s left on a doorknob, which is slightly different. 

“It’s still the idea that something happened in the corner of your eye, but you didn’t quite know what it was. And the assassin who laid it is long dead now.”

The good news is season 7 is definitely going ahead and has already been filmed, so we can expect the next chapter to land around the same time next year. 

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Featured image credit: Apple TV