The Slow Horses season 6 finale is out now, and its shocking ending is explained by new showrunner Gaby Chiappe in an interview. Apple has also debuted the first trailer for season 7.
The season was marked by a high number of character deaths, and the finale continued that trend with the death of Emma Flyte at the hands of River's father, Frank Harkness. In the episode's final moments, another character seemingly dies in far more shocking fashion: River Cartwright. It is not entirely clear what caused the death. According to head writer and season 6 showrunner Gaby Chiappe, the groundwork is laid in Episode 2, when assassins Jim and Jane come knocking while River and Sid are hiding. Jim spots a small bottle on the table and the crowbar River brought in, and the implication is that he coated the crowbar with its contents, a Novichok attack given the nerve agent attacks seen elsewhere.
Chiappe said the team debated whether audiences would understand what was happening. The idea comes from the book, where the substance is left on a doorknob instead. The concept remains the same: something happens at the edge of your vision, and you do not quite know what it was. The assassin who laid it is long dead.
Chiappe does not technically confirm River's death, but the season 7 trailer, which airs at the end of the finale, strongly suggests it. Apple has renewed Slow Horses through season 8, and season 7 has finished filming, with an air date expected around September 2027.
Source: 9to5Mac · Summarized by HeadlinesBriefing