‘Slow Horses’ Boss Reveals River & Sid Kiss Was Improvised by Stars (Exclusive)

Slow Horses is heading into its sixth season finale with River (Jack Lowden) putting himself in danger for Sid (Olivia Cooke) — after the two share a major moment that co-producer Gaby Chiappe tells TV Insider wasn’t in the script. Warning: Spoilers for Slow Horses Season 6 Episode 5 ahead!

This is a great episode to showcase just how well River and Sid work together, first dispatching the assassin trying to kill her, then both of them, then once Diana (Kristin Scott Thomas) makes a deal that would put Sid on a plane to her death. First Desk claims that she’s handing her off to the GRU to de-escalate the situation after using her ID for an off-books hit, but it’ll only take a couple months at most to sort it out. She can’t afford to lose the agent who actually carried out the hit. But Sid knows they’ll kill her.

“I love it. And then the actors improvised it. That wasn’t in the script. I think they thought they needed it, and I thought it was absolutely brilliant when they did it,” Chiappe reveals to TV Insider. “The kiss came from them. It’s very lovely.”

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That moment comes after a significant conversation the two shared while being held and waiting to be taken to the plane. Sid admits that when the assassins first came looking for her, River was the only person she could think to go to for help. She says his grandfather’s house felt like home, and River shares how his grandfather used to leave a light on when he was expecting him.

While that’s just who River is, it’s also because it’s Sid specifically that he does that, says Chiappe. “I think he’s got a very old-fashioned chivalric streak, River, and he does want to do the right thing always, but there is also the fact that it’s her, both those things. All of those things are true. It’s a kind of perfect storm of he can’t let this happen.”

As for what to expect in the October 21 finale, “It’s like a sort of gathering storm. Everything is coming to bear on where everybody is gathered in that one house and all hell is coming for them,” the co-producer warns. “And we know that Slow Horses, people die, so you don’t think Coe (Tom Brooke) is necessarily going to be the last on that body count. And who comes away from that and how is very much worth watching for, I would say.”

What did you think of that kiss? What are your predictions for the finale? Let us know in the comments section below.

Slow Horses, Season 6 Finale, Wednesday, October 21, Apple TV