Slow Horses season 4 episode 1 ending spoilers follow.
The premiere episode of this season of Slow Horses starts and ends with a violent bang – first, there's a bomber at a London shopping centre and then finally, a bullet rings out from David Cartwright's shotgun.
Heartbreakingly, River's grandfather's apparent dementia has worsened in the months since season three. He visits his club in London and is confused when he's turned away, having forgotten he cancelled the membership.
Based on Mick Heron's book Spook Street, the fourth season of Slow Horses questions what happens when a spy starts to lose their grasp on things – and the many secrets they have kept.
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In the first episode of the Apple TV+ hit, River (Jack Lowden) admits to Louisa (Rosalind Eleazar) that he has started putting off visiting his grandfather, because he occasionally doesn't know who he is. She then encourages him to go to his countryside home that night.
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But when we see someone arrive claiming to be River, David is clearly confused and unsure whether this man who heads upstairs to run him a bath is indeed his grandson.
Who does David Cartwright kill?
When David enters the bathroom and shoots the man insisting he is River, we never actually get a look at him to see for ourselves.
Then, when Jackson Lamb (Gary Oldman) arrives on the scene later – David having scarpered – he identifies the now faceless body as his own Slow Horse.
The possibility that River met his demise is heightened during the episode by comments Oldman made ahead of this season, teasing a major character could "cop it" during an interview with the Radio Times.
But fear not! It isn't River, as we finally learn in the closing scene of the episode when he drives through the French countryside in a taxi, presumably to figure out what's afoot.
If we delve into the plot of Heron's fourth book in the Slow Horses series – warning, Spook Street spoilers ahead – the man who actually met his end in the bathroom is connected to an old mission from David's Cold War past while heading up MI5.
However, the show may have changed the plot of the book in certain ways. We'll just have to tune in next week to see what happens next.
Slow Horses season 4 is streaming on Apple TV+.
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Previously Deputy TV Editor at Digital Spy and, before that, a TV Reporter at The Mirror, Rebecca can now be found crafting expert analysis of the TV landscape, when she's not talking on the BBC or Times Radio about everything from the latest season of Bridgerton or The White Lotus to whatever chaos is unfolding in the various Love Island villas. When she's not bingeing a boxset, in-the-wild sightings of Rebecca have included stints on the National TV Awards and BAFTAs red carpets, and post-match video explainers of the reality TV we're all watching.
