Episode 3 opens with River Cartwright (Jack Lowden) held hostage in the box room of a French home. “Someone is coming to talk to you,” his shotgun-wielding kidnapper tells him. We don’t learn any more, though, before action cuts to Standish’s flat and a very confused David Cartwright (Jonathan Pryce).

*Warning – contains spoilers for Slow Horses season 4 episode 3*

‘My fault, it’s all my fault’

Cartwright’s desperate to speak to First Desk as he needs to tell them about River and “what’s coming”. Standish (Saskia Reeves) tries to soothe him in what turns out to be an uncharacteristically touching Slow Horses moment, before he blasts: “What would you know, you’re only a secretary.”

We leave them with Standish promising to call and make the first appointment she can for him to meet with First Desk and David muttering “my fault, it’s all my fault”. We’re beginning to think that maybe perhaps it is…

The Slow Horses meet their match?

Back at Slough House, Flyte (Ruth Bradley) is waiting in Jackson Lamb’s office.

Move David Cartwright, he instructs Louisa (Rosalind Eleazar) as Flyte tells Lamb she’s bringing River in. “Be my guest, I don’t know where the fuck he is,” he tells her, before she cuffs him and tells Lamb she’s taking him to The Park for questioning. Asked if the cuffs are absolutely necessary, she proves more than a match for Lamb’s sarcasm and tells him: “I’d rather not take my chances with a man who looks like he gropes people on buses.”

Lamb pretends he’s happy to surrender David Cartwright to avoid being taken to The Park, telling Flyte he’s at Standish’s flat, so she uncuffs him and heads out – but not before cuffing a very flirty Roddy to the gym equipment he’s installed in his office. Have the Slow Horses finally met their match? Somehow we doubt it… Flyte heads to Standish’s flat looking for Cartwright but she’s already stashed him elsewhere. However, when she goes to retrieve him, Cartwright Snr has legged it out the back door…

Park life

Over at The Park, First Desk Whelan (James Callis) is plotting to bring down Taverner (Kristin Scott Thomas). He enlists a starstruck Giti (Kiran Sonia Sawar) to help, taking her down to the records department to look for other “cold bodies”. Met with resistance from Molly (Naomi Wirthner), who says she doesn’t want to get in the middle of First and Second Desk games, he asks her: “Who do you think comes first when I say First Desk then Second Desk?” “Diana Taverner,” she tells him deadpan. And we can’t help but agree…

Is River one of Winters’ brothers?

Meanwhile, back in France, we rejoin River and the person who was coming to speak to him – his dead doppelganger Bertrand’s mum. Showing her the hunting picture that also includes Robert Winters, she confirms that they are actually brothers, just like Winters said in his chilling video.

It turns out Frank Harkness fathered an army of children with young girls who were never allowed to see their babies. With the women out of the picture, he then went on to turn them into trained killers. “Russians, Greeks, one other local girl, an English girl,” she tells River of the mothers. “They have his children then he makes the mothers leave.”

As the episode is called Penny For Your Thoughts, we’ll give you ours… Now, we know River was brought up by his grandparents, and that his parents were out of the picture. He also bears more than a passing resemblance to Bertrand (before he was shot in the face, obvs). And David Cartwright is linked to France somehow… So could River’s biological dad be Harkness? Is River unknowingly one of the brothers? Did David Cartwright rescue him as a child and that’s what kicked all of this off? It might sound like a stretch, but this is Slow Horses, after all, and anything can happen!

Bad Sam Chapman returns

However, while there’s no hint that David Cartwright ever went to France, Lamb is told that Sam Chapman definitely did. And the former MI5 agent is back in this episode. Turns out he’s the “old man” the French assassin and Frank Harkness were talking about killing way back in episode one.

“Someone tried to whack David Cartwright,” Lamb tells Chapman on the phone. “Did anyone come looking for you?” Chapman asks Lamb, hinting at his involvement in whatever went down. Someone came looking for Chapman, though, as he tells Lamb he’s being tailed. Lamb tasks the Slow Horses with tailing the tail (the French assassin), who’s on the phone to Harkness. “Kill him out of sight and move on to Cartwright,” he tells the shooter as he follows Chapman through a busy London market, evading the Slow Horses (and pushing Marcus through a shop window) before the pair end up in a deserted garage.

He’s just about to pull the trigger on Chapman when Dander (Aimee-Ffion Edwards) comes in brandishing some glass from the shop window. She’s quickly knocked out by the assassin, though. Next up is Marcus, who’s floored by a shelving unit. Which means Lamb has to come to the rescue, saving the day – and Chapman’s skin – by stealing a London Taxi, driving it into the garage and running over the French assassin.

“You alright?” he asks Dander as she stumbles to her feet. “I’ll deal with the roadkill,” says Lamb. However, as he heads to the back of the taxi, looking for a body, the assassin has disappeared… Living to fight another day and doubtless carry on his less-than-impressive assassin duties in episode four next week.

New episodes of Slow Horses drop on Apple TV+ every Wednesday.