In perfect fashion for its collection of castoffs, Slow Horses Season 6 begins with a payroll error. For some reason, no one at Slough House got a paycheck. By the end of the season, bodies, tragedies, and property damage have stacked up like cordwood. Which, if one thinks about it, is also pretty perfect for Jackson Lamb’s (Gary Oldman) Joes.

While all of that is bad news for Slough—again, fittingly—it is great news for viewers. After a Season 5 stumble—still good but definitely the series’ weakest offering—Slow Horses Season 6 returns to tiptop form, with Adam Randall, director of Season 4, back at the helm. Like his prior season, Randall seems especially concerned with the family—found and literal—aspects of the show. He mines that even more effectively here, delivering the show’s most emotionally brutal chapter to date.

As the current team from Slough House attends the funeral for David Cartwright (Jonathan Pryce)—the master spy and River’s (Jack Lowden) beloved grandfather—someone is killing former Horses. With River’s father Frank (Hugo Weaving) coincidentally back on British soil, the who of it, if not exactly the why, seems obvious. Diana Taverner (Kristin Scott Thomas) is even less interested in Slough House’s plight than usual. She doesn’t even bother to give Lamb a heads-up about what’s happening. Or perhaps it is something more than indifference. After all, Emma Flyte’s (Ruth Bradley) choice to call her boss on it is met with considerable hostility.

In past reviews, I’ve made it clear that Lamb’s flatulent gross-out countenance, a weapon in his spy arsenal or not, is not exactly my speed. I tolerate, never mind enjoy, the character almost entirely because of Oldman’s considerable talents. This may be his best turn yet as Lamb. That’s a considerable relief after he ladled on both the cruelty and grossness a bit too liberally last season. One of the keys to him, that Oldman brings fully into relief this season, is his loyalty. After at least one prominent betrayal of a colleague in his past, he seems nearly blindly devoted to those in his circle. His relationship with Taverner is particularly illustrative. Even as Thomas makes her as cold and calculating as she’s ever been—while still somehow giving us glimpses of humanity—Lamb still throws her a proverbial lifesaver.

The team is also head and shoulders more effective this time out despite being perhaps more out of their depth than ever. After last season’s bumbling—often funny but ultimately too much—it is nice to see the Horses again demonstrate that a corrupt, unyielding system has pushed them into Slough House exile, not true incompetence.

However, this season’s true (top) secret weapon is the show’s heart. While always a bittersweet affair, Slow Horses Season 6 feels especially vulnerable. David’s funeral, the show’s first big setpiece, sets the tone. New head writer Gaby Chiappe and the rest of the writers’ room lace it throughout the episodes that follow. As a result, even the likes of reliably horny Roddy (Christopher Chung) exhibit moments of unexpected depth. The show has always been at its best when it recognizes that the pain of the spy game and the ridiculousness of its excesses coexist. When done right, they sharpen each other rather than undermine one another. Slow Horses Season 6 captures that balance wonderfully, delivering a sadder and less predictable effort without losing its sense of humor.

Slow Horses Season 6 enters AppleTV’s corral on September 16.

Watch the Slow Horses Season 6 Trailer now: