Slow Horses writer explains real reason River Cartwright doesn’t kill his murderous dad Frank

River Cartwright had every reason to hate his father, Frank Harkness, but when the two finally came face to face in the Slow Horses season 6 finale, River chose not to kill him. So, why didn’t River Cartwright kill his father Frank when he had the chance in Slow Horses season 6 ending?

River finally confronts Frank after learning more about the man behind the violence. Frank is a ruthless killer, and River has spent much of the season caught up in the deadly consequences of his father’s actions. But when River gets the opportunity to shoot him, he doesn’t pull the trigger. Instead, Frank leaves, with his future still uncertain.

Gaby Chiappe, who wrote the finale and served as season 6 head writer, said that the decision came down to what felt right for River as a character. And their complicated relationship makes the scene even more interesting.

Why doesn’t River kill Frank Harkness?

Speaking to Gold Derby, Chiappe explained why the writers chose this ending, which differs from Mick Herron’s original novel.

She said, “That scene doesn’t exist in the book, but I don’t think anybody could believe River shooting Frank at close range, face to face. Also, River’s not in a state to pursue him, but Frank’s pretty beat up at that point. He’s letting him go, but where’s he gonna go? We don’t know. It’s Frank. He could live to fight another day, but you never know with him.”

One of the most interesting things about the finale is that River and Frank seem to have a stronger connection than either of them would like to admit. River hates what his father represents. Frank is a psychopathic killer, and River has had to deal with the damage his father has caused. Yet River is also clearly affected by their relationship, and Frank seems more interested in his son than he lets on.

Chiappe explained this tension while discussing a scene in Episode 4, when Frank speaks to Jackson Lamb about the attacks on the Slough House agents.

She said, “And Frank behaves as if he cares not at all about River, yet in that scene in the Shake Shack in the fourth episode where he’s talking to Lamb and Lamb says that people have been killing slow horses, Frank says, ‘Did they get anyone I know?’ River’s his first thought, you know?”

She then added, “There is a sense in both of them that they are connected; they may think they have contempt for each other, but the picture is a little bit more complicated than that.”

Frank also leaves River with a warning about his grandfather

Before Frank walks away, he tells River to look to his grandfather, David Cartwright, for his education. At first, this might sound like Frank is simply trying to get under River’s skin. However, there’s a darker meaning behind the comment.

River has always idolised his grandfather, seeing him as a much better man than his father. Frank challenges that view by suggesting that David’s past wasn’t nearly as innocent as River might believe.

Chiappe explained that Frank’s words are meant to point River towards the truth about his grandfather.

She said, “We’ve had lots of hints of this before that David Cartwright was a loving grandfather to River, but somewhere else in one of the books it says he was up to his cardiganed elbows in blood.”

She continued, “He was not a benign, kindly presence; he did bad things and those things have affected quite a lot of people, like Jackson Lamb, for example.”

Frank’s fate remains uncertain after the season 6 finale. River lets him go, and Chiappe doesn’t rule out the possibility that he could return. As she put it, “He could live to fight another day, but you never know with him.”

For all the latest film and TV updates and hot takes, like our Facebook page.