If you're a fan of big-budget, witty spy thrillers starring Hollywood actors, you're in for a treat. Right now, there's an abundance of choices. In just the last few weeks, Eddie Redmayne has been taking on rightwing politicians in "The Day of the Jackal," and Ben Whishaw has been shooting those with a quizzical look in "Black Doves." While these are entertaining, none can quite compare to the charmingly worn and occasionally fart-joking "Slow Horses."

Slow Horses: A Slow Burn to Fame

It took four seasons for "Slow Horses" to become one of the most talked-about TV series. The fact that such an immediate show has proven to be a slow burn is quite odd, but the attention it has received is well-deserved. From the very beginning, it has been excellent. Some might argue that it was even more outstanding at the start, but even when "Slow Horses" is on cruise control, it remains one of the finest thrillers on television. Gary Oldman delivers a career-defining performance as the aggressively flatulent Jackson Lamb. Lamb is an old-school spy whose traditional methods have been sidelined in favor of a new, public-facing MI5 culture. But over the course of four series, he has transformed into a man capable of near-superhero levels of espionage and combat, given the chance to finish his takeaway first.

The Start of Season Four

Season four begins with a purposeful bang as a suicide bomber drives a car filled with explosives into a shopping center in the middle of London. This is reminiscent of the very first episode when River Cartwright (Jack Lowden) fumbled a training exercise at Heathrow. But this time, it's no training exercise; there's a real bomb. The attack sets off a chain of events that had been hinted at since the beginning of "Slow Horses." River Cartwright's elderly grandfather David (Jonathan Pryce) poses the serious question of what happens when a man entrusted with the darkest of state secrets loses the cognitive ability to keep them to himself.

The Cock-Up and Its Management

The bombing also instigates a major mess that must be managed by Diana Taverner (Kristin Scott Thomas). Technically, she has been demoted to Second Chair, but it's clear who the real First Chair is, especially when the man in the hot seat is Claude (James Callis), a comically dim-witted government plant with no idea what's going on. It's up to the renegades and misfits of Slough House, all supposedly decent spies with a habit of sabotaging their own careers, to figure out what's happening and how to stop it. The terrorist storyline spreads beyond the UK to France, involving a bizarre conspiracy with politically motivated mercenary breeding. Before that, there's a fake key character's death that sends MI5's "dogs" on a satisfying wild goose chase. Newcomer Ruth Bradley, playing a new chief dog who mistakenly thinks she has Lamb figured out, is a welcome addition.

The Personal Touch of Season Four

This may be the most personal season of "Slow Horses" yet. Junior Cartwright is taken more seriously, and his relationships with his grandfather and the eternally cynical Lamb are given more emotional depth. The snippy friendship between Shirley and Marcus also develops, and when their poor decision-making comes back to haunt one of them, it creates those gut-wrenching moments that "Slow Horses" does so well. The against-all-odds mentality doesn't always lead to success.

The Essence of Slow Horses

Despite the emotions, "Slow Horses" works because it remains true to its name. Lamb does his own thing, and Taverner reluctantly goes along with it. It downplays the glamour of spying while reveling in its own grimy glory. In an era of streaming bloat, "Slow Horses" is lean, to the point, and often very funny. There are no 90-minute mid-season episodes here, no drawn-out subplots to pad out the run length. What you see isn't exactly what you get; this is spycraft after all. But what you expect from "Slow Horses" is generous entertainment, and it continues to deliver in spades.