‘Slow Horses’ Boss Breaks Down Shocking Finale & Teases What’s Next in Season 5

[Warning: The below contains MAJOR spoilers for the Slow Horses Season 4 finale “Hello Goodbye.”]

Slow Horses stages the worst father-son reunion in the Season 4 finale for River (Jack Lowden). Jackson Lamb (Gary Oldman) as his father figure doesn’t look so bad anymore!

It turns out mercenary Frank Harkness (Hugo Weaving) is River’s father—and he puts a grenade in the hood of his son’s jacket as MI5 is moving in! Frank does eventually end up in an interrogation room, but he’s not worried; he knows he won’t be spending too long there. Meanwhile, Patrice’s (Tom Wozniczka) assault on Slough House results in Marcus’ (Kadiff Kirwan) death, and River moves his grandfather David (Jonathan Pryce) into a care home.

Below, showrunner Will Smith talks about those and more major moments from the Season 4 finale and teases what’s ahead in Season 5.

Talk about bringing in River’s father, what you wanted to do there, and where you wanted to leave River as a result of that.

Will Smith: The kind of arc of the season for River, and it is an interesting one. And one of the things I love about the show is each season has a different kind of emphasis, and obviously, you’re bringing in different characters and saying goodbye to some others—but it just felt really fresh and interesting to have a series where River is not in Slough House at all, has one scene with a Slow Horse, which is Louisa [Guy, who plays Rosalind], and then is on his own for the whole time. And one scene with Lamb at the end, which we did shoot without any dialogue at all, but then felt that didn’t quite work with the ending that we wanted. We want to give a slight lift after the really sad care home scene. And also people, you kind of think, have waited all season to see Gary and Jack together, so let’s not have them say nothing.

But yeah, really this season is about River losing his grandfather and losing the kind of haloed image he has of his grandfather as this saintly master spy and realizing that he was involved in some darker things and bent the rules and also lied to River and concealed the truth of his parentage from him. So it’s losing his grandfather, finding his father, realizing he’s a maniac, and being left with Lamb as the only kind of father figure in his life. And so it’s very disorientating. It’s a hell of a couple of days for River.

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What does that mean for him going forward? How is he processing all this? Is he going to be throwing himself into his work?

Yeah, that’s a great question. Exactly. That’s what I  talked to Jack about for Series 5, which we’ve nearly finished. He’s haunted by it. He’s unsettled by it. He’s throwing himself into exercise more and he’s not properly focused. It’s thrown him and it’s kind of haunting him and people do call him out on that and then he tries to address it. But yeah, we carry the consequences forward.

And where did you want to leave Jackson heading into Season 5? You start this season with him thinking he lost a member of Slough House then end it with him losing one.

Yeah, we do. And it’s not just Marcus he loses. He loses Sam [Sean Gilder]. And when you think about it, there’s only two people that you ever see Lamb showing any kind of respect or kind of vague affection towards, and that’s Sam and Molly [Naomi Wirthner]. You think she’s going to go at one point and Sam does go. It’s one of my favorite scenes where Lamb finds Sam’s body. I think Gary was just incredible. I mean, he’s always incredible, but that particular scene, the kind of power and the churn that you saw under Lamb and the little pat he gives him when he leaves and then the switch as he leaves the room and grabs the whiskey bottle. He’s going to get revenge for this.

Lamb is kind of battered when we meet him in Series 1. I think Lamb is a kind of living cautionary tale of what life as a spy will do to you. And he’s seen a lot of loss and he’s sort of blasé about it, but it is probably not affecting him as much as it used to because maybe he’s numb to it. But I think when he’s misidentifying River’s corpse, he’s kind of doing that in that way to kind of throw Flyte [Ruth Bradley] off unbalance and also to just sell the lie that it is River. But I’m not sure that his reaction would be that different if it really was River, because he knows if people are going to swim in these waters, that’s the risk they run.

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Talk about killing off Marcus in the way that you did.

We didn’t want to show the moment because you want to—it’s awful. You want to make it as bad as possible for the audience really. It’s not sadism. You just want to wring the most emotion out of it without it being melodramatic. You just want—certainly when I watch stuff—to feel stuff and it just felt that if you hear the shot and you don’t know if it’s him or not, you’ve got that moment with Shirley [Aimee-Ffion Edwards] where you’re like, maybe he’s okay. And then Patrice comes in and it looks like Shirley’s going to die, and then Lamb turns up and they overpower him. So it’s the audience finding out the confirmation that Marcus is dead at the same time as Shirley, and so it’s a double loss really. It’s like, oh my God, we’ve lost Marcus, and we love Marcus as a character and oh my God, what’s this going to do to Shirley? And so splitting those two moments just felt like you get the most impact from that. And then Shirley being denied—Coe [Tom Brooke ] talking her down from, “Don’t shoot him, it won’t bring you peace,” and her really wanting to do it and then him just doing it anyways, yeah, it just makes it harder.

Frank is sitting there in the interrogation room so certain he’s going to be let go. What can you say about his future and what do you enjoy most about bringing him in to put multiple characters in uncomfortable positions as a result?

Yeah, that’s the fun of Frank is he is disrupting everything. He’s shaking it up. He’s changing River’s entire perception of or fact of who he is. It’s great to see him in that scene with Taverner [Kristin Scott Thomas] just be so dismissive of her. We’ve always seen her just completely own people in those kind of situations, and he’s just not bothered. Because he knows, “I’ve done killing for you, I’ve done killing for everyone, you’re going to have to let me go.” And so it just is the kind of arrogance, which is really kind of unnerving, I think, and having him walk out into the world. And he’s kind of a specter in the next series, but he appears in the later book. So he’s out there waiting. It’s clearly unfinished business with him and River. I mean, he put a grenade in his hood, and yes, River caught him, but it’s ongoing and Frank is a menace. He’s going to have to be dealt with at some point.

So he’s more so just hanging over their heads off-screen in Season 5?

Yes. Where we start in Series 5 is emotionally River and Shirley are both struggling with the fallout of what happened in the final episode of Series 4.

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What can you say about who’s coming back? I’m assuming everyone in Slough House who’s still alive and Diana, right?

Yes.

What about Claude (James Callis)?

Oh, Claude is still there. And Claude was just a wonderful, again, great sort of disruptor character. And I just love ending Series 3 with Taverner thinking, I finally got the job I always wanted, and then you start Series 4 and have a kind of momentary fake-out that she got the job and then, oh, no, she didn’t. And then she lost it to somebody who’s just so beneath her and so out of his depth and she’s having to pick up his mess the whole time. And it just changed—I think I have to slightly speak for Kristen here, but it just felt like watching them that she really loved doing those scenes with him because it was just something very different for Tavener and having to play the concealed irritation and also just for the audience, it’s an experience that I’m sure every woman can relate to of, oh God, I’ve got this idiot man above me to contend with. And James is just superb and just totally landed the tone of the show and just, I mean, we’re very lucky. Everyone who comes in just seems to seamlessly go like they’ve been in it forever. Ruth Bradley who played Flyte was the same, and Hugo obviously was same, Tom Brook who played Coe, Joanna Scanlan who’s Moira. We do have an amazing casting director, so that helps.

What can you say about next season’s case in comparison to the cases that we’ve seen so far? How is it challenging the team more?

They’re all slightly different. Series 1 is in some ways the most straightforward, and then it was a sort of kidnap plot, but then obviously the twist that Taverner is behind it. And then Series 2 is Cold War scores being settled and impacting on the present. And then Series 3 was Catherine [Saskia Reeves] being taken and then a more action-based climax than we’ve done before. And the challenge there was to keep the tone of the show and not just feel it was sort of generic in any way. And Series 4 is the most personal story. So in many ways, it’s the most raw kind of story, the most emotionally affecting, probably the most brutal in terms of the action in that in Series 3 you had sort overwhelming numbers of people attacking the Slow Horses, but it was the number of people, not the quality of the soldiers. Whereas in this, you’ve got one guy and he’s just like a Terminator. It was Patrice—brilliant Tom who was playing him—and so it just had a brutality to it.

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And then Series 5, the plot kicks off and it’s sort of centered more around Roddy Ho [Christopher Chung], which is obviously going to have a kind of different tone to the harder tone of Series 4. Series 5, I’m super excited by. I’ve only got a couple days to film, but it’s got some twisty espionage stuff and it’s got a lot of stuff that people love about Slow Horses and then some new stuff that we’ve not done before. So I’m very excited about that.

I have to say how good the Jackson-Standish dynamic is.

Yeah, I love her character and I love Saskia. She’s the most amazing actor. She’s back [in some capacity after leaving Slough House]. Catherine and Lamb are locked into some twisted codependency because of their shared kind of betrayal and grief and hurt at the Charles Partner. They’ve not ever fully discussed it, and she doesn’t even know the full details. And in some ways, I feel he lashes out at her because it’s kind of self-loathing at him being fooled by Partner, and she’s a reminder of that. So he’s sort of punishing himself by having her remind him, and it’s a very twisted relationship. But there’s something, I don’t know, it is fascinating, and they’re both fascinating characters because there’s obviously so much backstory there for both of them, and they’re such amazing actors that you can see the backstories there under them. They’re carrying the weight of their years and their experience. That’s what those actors are doing, is you can feel there’s so much stuff there to come out.

Slow Horses, Season 5, TBA, Apple TV+