Welcome back to Slough House, as season 4 of AppleTV+ drama Slow Horses bolts out of the gate. When a car bomb explodes in a crowded shopping center, nerves are frayed, but the situation worsens when it’s revealed that the attacker was using an MI5-created identity. The case finds River Cartwright (Jack Lowden) and his grandfather David (Jonathan Pryce), a former high-ranking intelligence officer now struggling with dementia, which makes him increasingly paranoid.
The revelation that David once had dealings with the group behind the bombing, and his ability to identify their leader (Hugo Weaving), puts both him and River in jeopardy. With David’s deteriorating memory leaving him disoriented, River finds himself largely on his own. As a result, Jackson Lamb’s (Oldman) slow horses are inevitably drawn into yet another high-stakes operation, one that far exceeds their usual capabilities and threatens significant consequences.
As with previous installments, this season intertwines two storylines that eventually converge as the connections between the mysteries are revealed. At the park, Kristin Scott Thomas’s Taverner and her team are investigating the terrorist attack, trying to assess the risk of another bomb. True to form, Taverner remains as unpredictable as ever, especially when her reputation is at stake. She is prepared to go to any lengths—literally anything—to safeguard it. The revelations about MI5 in this season are as compelling as the case itself, particularly with the introduction of a new player in the mix.
We meet three new faces at Slough House this season: Tom Brooke’s enigmatic hooded character, Joanna Scanlan’s secretary who feels she’s entitled to more, and Ruth Bradley’s no-nonsense head of the dogs who, while not officially part of the office, is frequently drawn into their escapades. Each of these newcomers shines in their role, particularly Scanlan’s Moira, who is eager to uncover the reason for her assignment to Slough House.
One of the pleasures of Slow Horses, and a key reason it resonates with viewers, is its skillful blend of intense drama with a sharp sense of humor. While this balance remains in Season 4, the tone is notably more personal and, as a result, feels more impactful than previous seasons. The show has never shied away from extremes or placing its characters in peril (as evidenced by the numerous deaths we’ve witnessed), but this season feels distinct due to the persistent threat of personal tragedy.
Even if River manages to protect David from his attackers, he cannot halt the relentless progress of dementia. While the series still offers moments of humor, and Roddy (Christopher Chung) continues to provide comic relief—the deeper exploration of River and David’s lives adds a sobering dimension, highlighting the real stakes involved.
Another excellent season. Slow Horses is available now on AppleTV+.
