‘Slow Horses’ Season 6 finale kills Emma Flyte and leaves River Cartwright’s fate open

For River’s cliffhanger, Chiappe pointed Gold Derby back to Episode 2. Assassin Jim sees a small bottle and the crowbar River brought into the house. “We have to assume that he paints it with what’s in the bottle,” Chiappe said. River moves the crowbar in the final scene before his hand shakes and he collapses. Vulture’s recap also connects his collapse to poisonous residue on it.

Asked by TV Insider whether River is dead, Chiappe said, “We don’t know what’s going to happen to him.” She suspects the agent is Novichok and noted that people can survive it or die from it. Vulture reports that River survives the poisoning in Herron’s novel Slough House, while distinguishing that outcome from what the television series might do.