Slow Horses was something of a slow-burning surprise when its first season launched back in April. It was yet another Apple TV hit whose marketing hadn’t done well enough to connect with audiences, relying instead on word of mouth. What viewers found, however, was a low-stakes spy drama with the sort of pulpy, throwback thrills that you rarely see in our more self-serious age. Mixed with a shot or two of black comedy, and it made for a surprisingly gripping package I felt compelled to rave about back in April.

The show’s second season, which returns to Apple TV+ on December 2nd, carries on in that vein, albeit with less of the show’s trademark humor. It focuses, once again, on the staff members of Slough House, the closest thing MI5 has to purgatory for disgraced intelligence officers. Led by the “colorful” Jackson Lamb, the Slow Horses are often left doing administrative donkeywork nobody else thinks is worth doing. Of course, you wouldn’t have a series if the misfits weren’t frequently embroiled in the grander machinations of the intelligence community.

Season Two is based on Dead Lions, the second in Herron’s series of Slough House novels, and focuses on Lamb’s investigation of the death of a former officer. Apple’s usual ban on spoilers means that, of the plot, I can only say that it features “long-buried Cold War secrets” which “threaten to bring carnage to the streets of London.” Oh, and that “when a liaison with Russian villains takes a fatal turn, our hapless heroes must overcome their individual failings and raise their spy game in a race to prevent a catastrophic incident.”

We pick up shortly after the first season, with the Horses frustrated that their heroics haven’t led to better things. Instead, the team has been bolstered with Shirley Dander (Aimee-Ffion Edwards) and Marcus Longridge (Kadiff Kirwan) and put back on regular duties. That has, understandably, left River Cartwright (Jack Lowden) in something of a funk. But when a former agent is found dead on a bus, it suddenly piques Jackson Lamb’s (Gary Oldman) interest enough to return to work in the field.

Given that the first two six-episode seasons were shot in a single run, it’s no surprise that the show expects you to recall much of what happened in the first run. But, despite the continuous production, there’s a big tonal shift here, with the show getting darker and dropping some of its trademark wit and humor. And, I’ll be honest, the running gag about Jackson Lamb’s lack of personal hygiene and non-stop farting starts to get a bit thin by the end.

Fans of the books will already know why the series takes a darker turn, although I found some of the twists were initially a bit lightweight. Maybe years of watching series where nothing we see can be believed meant I was always waiting for a non-existent second shoe to drop. None exist here in the Slow Horses universe, and when you see some beloved characters go, uh, to places you might not expect, be mindful that none of it is for show.

It’s not a show that you can watch with one eye on your phone, but it’s so briskly paced that if you blink, you might lose your place. I’d consider myself a close watcher of things, but even I found myself having to pause to work out which sinister Russian emigre was which. It doesn’t help that while you can see where all of the various plotlines are heading, their collision is a little predictable. But I’m nitpicking, and this isn’t the sort of show you need to unpick for hours on end on Reddit – just repeat to yourself it’s just a show, and you should really just relax.

And Slow Horses’ second season really belongs to Rosalind Eleazar (Guy) and Saskia Reeves (Standish), who are both given time and space to grow their characters. The former carries much of the major narrative this time around, while the latter again shows how much steel is buried underneath Standish’s downtrodden personae. But the show is democratic enough to give every character a grace note or two during the explosive, and gripping, finale.