Slow Horses season 4 review: "Apple TV's masterful spy drama remains one of the best shows on right now"

Apple TV’s masterful spy drama series Slow Horses has always known how to kick off a season in style. Who could forget the thrilling Stansted Airport set piece from the first installment? Or the second season beginning with the mysterious death of former agent Dickie Bow? More recently, season 3 impressed only minutes in with a James Bond-esque chase through the streets of Istanbul. All these opening scenes are immediately gripping, but the secret to the show’s success is the fact that each season only gets better from there. Thankfully, the same can be said for the upcoming fourth season.

Adapted from author Mick Herron’s fourth novel in the Slough House book series, titled Spook Street, we rejoin our not-so-merry band of dysfunctional MI5 agents as the threat levels in the UK reach a critical point following a suicide bomber targeting a shopping mall. That’s only the start of the story though, as our misfits are pulled into a case that is the show’s most personal one yet.

Spook Street

Just like with previous chapters, two storylines run concurrently here before seamlessly coming together as the connections between the mysteries are uncovered. At the park, Kristin Scott Thomas’ Taverner and co. are busy looking into the terrorist attack, trying to figure out if another bomb is likely. However, this is Taverner we are talking about, who – as ever – remains full of surprises, particularly when her reputation comes under threat. She is willing to do anything – and I really do mean anything – to protect it. The secrets about MI5 that are uncovered here are as intriguing as the case itself, which is especially true as a new player enters the ring.

That’s because this season, Thomas’ notoriously haughty Second Desk agent is also having to babysit newcomer James Callis’ Claude Whelan, a bumbling fool who has somehow landed himself the job of First Desk at MI5. Watching the condescending Taverner having to deal with Claude’s idiotic nonsense is delicious and adds a brilliant new dynamic for the show, particularly when it’s revealed that Whelan may not be the moron we first assumed he was. Let’s just say we can only hope to get more from the pair in future seasons of the show.

This time it's personal

Whilst the terrorist plot is indeed thrilling, it is significantly overshadowed by the second storyline which centers on the Cartwright family – Agent River (Jack Lowden) and his grandfather David (Jonathan Pryce). This season of Slow Horses really should come with the tagline 'this time it’s personal' as the show explores new emotional and intimate depths, with this arc’s laser focus on the Cartwrights raising the stakes like never before.

The always brilliant Lowden takes this in his stride, giving River a new edge as his grandfather’s life is threatened. Meanwhile, Pryce also comes into his own, finally being given meaty material after only ever popping up in previous episodes. With David struggling with his memory, Pryce delivers an incredibly affecting performance that will stay with you, recognizing that his character’s erratic nature is dangerous and terrifying, but also that these are the actions of an unwell man. It’s about time the writers put the spotlight on Pryce’s former agent and it’s also a relief to see it not go to waste.

On their journey, River and David clash with Hugo Weaving’s Frank Harkness, arguably the show’s best threat to date. Harkness is someone to be very afraid of, with his mere presence sending chills down the spine. Slow Horses isn’t the type of show to feature your usual run-of-the-mill villains, so what Weaving’s violent mob boss brings to the table is incredibly fresh and scary. Seriously though, the violence that ensues in his wake is gnarly (with a capital ‘g’) and it’s clear that the show’s stunt team enjoyed bringing these brutal fight scenes to life, with the action scenes always impressing.

The rejects

However, whilst it is great to see the focus shift to the Cartwrights, the rest of our beloved ‘rejects’ at Slough House are unfortunately sidelined. The likes of Gary Oldman’s Jackson Lamb, Christopher Chung’s Roddy Ho, Aimee-Ffion Edwards’ Shirley Dander, and Rosalind Eleazar’s Louisa Guy all have their moments, but they ultimately aren’t given too much to do this season. Which is a shame given that this hapless crew are the beating heart of Slow Horses, bringing warmth, emotion, and laughter to the truly great series. That’s not to say that isn’t present here as this season is still a complete joy to watch, but I just can’t help but feel we could have had more from them.

Especially since we have three newbies at Slough House: Tom Brooke’s mysterious hooded figure, Joanna Scanlan’s secretary who believes she deserves better, and Ruth Bradley’s matter of fact head of the dogs who doesn’t directly work at that office, but finds herself continually wrapped up in their antics all the same. This trio of additions are all excellent, especially Scanlan’s Moira who is desperate to know why she has been sent to Slough House – an enticing question we see a new character ask each season. The issue is the balance between old and new as our original favorites find themselves somewhat lost in the mix.

Despite this hiccup, it’s clear that Slow Horses is showing no signs of slowing down, delivering yet another charming and compelling season. It remains one of the best shows on TV right now and it’s quite frankly a crime it is still so underseen . But with a fifth season already filming, if you haven’t visited Slough House yourself yet, now is the time to do so.

Slow Horses season 4 premieres globally on Apple TV Plus on September 4 with new episodes airing weekly.

For more upcoming television that needs to be on your radar, here's our guide to the best new TV shows to watch out for.