Apple TV’s Emmy-winning spy drama Slow Horses ended its stellar sixth season with an action-packed finale, another devastating loss, and a potentially deadly cliffhanger that will leave viewers fearing for the fate of another fan-favorite character.

Based on Joe Country and Slough House — the sixth and seventh novels in Mick Herron’s book series — Slow Horses Season 6 showed Jackson Lamb (Sir Gary Oldman) and misfit MI5 agents past and present on the run from two Russian assassins (Kyle Soller and MyAnna Buring) and River’s dad, Frank Harkness (Hugo Weaving). Why? Taverner’s (Kristin Scott Thomas) Russia retaliation plan went wrong.

In Season 6, Episode 6, “Judgment Day,” Lamb finally schools the First Desk in a last-ditch effort to save his joes. So does Lamb’s plan work? Does Sid (Olivia Cooke) make it out alive thanks to River’s (Jack Lowden) grand romantic gesture? Who dies in Slow Horses Season 6’s finale? And what the fresh hell happens in that final jaw-dropping scene? Decider’s Slow Horses Season 6 ending explained has answers.

Read on for a detailed Slow Horses Season 6, Episode 6 recap. But just be warned, major spoilers await!

Slow Horses Season 6 Ending Explained: Slow Horses Season 6, Episode 6 Recap, “Judgment Day”

Slow Horses Season 6’s finale kicks off in the most chilling way possible. We hear humming from the other side of graffiti-covered bathroom stalls, where bloody Russian assassin Jane (MyAnna Buring) glues her car crash wounds and looks down at a marked map. As she resumes her mission — now fueled by a personal desire to avenge Jim’s (Kyle Soller) death — we check in with River, who’s being such a delightful little shit that the men who detained him after he kissed Sid and let her run free toss him out of their SUV and speed off. He calls Lamb and fills him in on Taverner’s attempt to hand Sid over to the GRU. But once he breaks the news that Coe (Tom Brooke) is dead, a newly spooked Lamb reminds River that Sid was a better agent than he was when she was in a coma and urges him to help the others.

Once River learns the rest of Slough House is holed up at Taverner’s holiday house with Reece (Lenny Rush), who his dad wants to kill, he races to their rescue after a familiar warning from Lamb: Moscow Rules, aka watch your back. As River heads for the safe house, Lamb sets Taverner straight: “The money you took from [Damien Cantor], it came from the top, and it came in rubles. Now he’s trying to kill anyone who can prove his connection to Natasha Carrington (Zrinka Cvitešić). The Russians are trying to kill the people they think are responsible for Kazan. And you know who’s in the crosshairs for both? My fucking joes.”

Taverner reveals plans to hand Sid over to the GRU, then head to the Home Secretary’s office and confess treason. “I’m first desk, and I’m compromised. I am the greatest threat to national security we’ve had in years, and I’m taking myself off the board,” she admits. Lamb orders her to save the Slow Horses first, and thankfully, he has a better plan. Lord knows the joes need it!

Back at the safe house the “fucking goldfish bowl”, River arrives solo and fills the team in on the GRU, Taverner setting Sid up, and the clean-up job. As Harkness and his mercenaries look on, plotting their attack from the tall grass outside, Lamb puts his plan into motion and crashes a birthday party for Natasha’s daughter. “I think the GRU has had you running an off-books assassination squad on British soil, because the man at the top wanted to settle scores,” Lamb tells Natasha. Now that that’s all gone tits up, who do you think is gonna take the rap, your boss, comrade Vassilly?” Lamb can tell Natasha wants out, and he wants the targets off of his joes, so he asks: “What if you could give Moscow the double agent mastermind behind Kazan?” When Natasha assures Lamb there is no double agent, he replies, “I’m not asking you if you’d buy it. I’m asking, can you sell it?”

Before we learn what Lamb’s got cooking, Shirley realizes Coe’s missing. River’s silence suggests their worst fear has been realized. And Coe’s “another one bites the dust” confirms it. As the group processes their grief and fear, a screaming match ensues, and Shirley starts putting everything out on the table. (She even accuses Louisa of stealing the diamond in Season 2!) Before all hell breaks loose in the group, the glass wall beside them shatters as Harkness and his men attack. Smoke fills the house, Molotov cocktails fly, and an all-out war commences. After temporarily taking down the mercenaries, an armed Flyte and Louisa cover the crew as they race through the tall grass down to a nearby beach. Roddy carries Reece to safety, and they take cover with Flyte and Shirley, while Moira, River, Standish, and Louisa hold up in a separate location.

As River wisely deduces, the group is “very very fucked,” and their only escape is back by the house. As the less experienced players in the strange, strange game hide out, Flyte, Shirley, and River head back in hopes of getting the car and taking out the hitmen. Though Flyte successfully kills one of Harkness’ accomplices, she runs out of bullets, and Harkness fatally shoots her on the beach. (NO!!!!!!!!!!!!!!!!! In the words of Ho: “What a legend!”) Louisa also takes a bullet from — SURPRISE! — assassin Jane. She’s back, and more determined than ever to annihilate River.

Shirley leaves Ho with Reece and tries to find them a boat to escape on. Instead, she finds “a godsend” weapon. But when she returns, Ho is gone. She teaches a terrified Reece how to shoot in case he has to defend himself, and after Ho sees Flyte was killed, he heads back just in time to shoot at one of Harkness’s men. There’s just one problem — well, two. Ho’s aim is shit, and he runs out of bullets. With a gun pointed straight at him, it seems like he’s next to bite the dust, until a shot rings out and a spear shoots through the mercenary’s back, courtesy of the young icon, Reece!

Before the bloodshed continues, we cut back to Cantor, who’s ushered into a recently emptied restaurant, where Taverner waits at the bar to carry out Part 2 of Lamb’s master plan. She tells Cantor she called in a bomb threat to clear the restaurant and save his life. From who? Russia. Lamb. Whoever gets him first. “Jackson Lamb knows I took money from you, and that your money is Russian money,” she explains, telling a horrified Cantor that she used his money to fund an off-books assassination on Russian soil and Lamb’s out for revenge. “Your car will take you to an airfield where a plane is waiting. The pilot has flight clearance for four different locations. I do not want to know which one you choose,” Taverner tells Cantor before claiming, “I can protect us as long as I remain first desk, and to do that I need you as far away as possible.”

A terrified Cantor obeys, but when he gets in his car, his driver Laslow isn’t behind the wheel. It’s Lamb, who drives him to the airfield where Sid and River parted ways. A plane is still waiting to take someone — anyone — to neutral ground to pay for Kazan. To spare Sid, Lamb makes Cantor the double-agent mastermind. And before he’s taken away, Cantor calls Harkness and orders him to stand down and abort his mission.

Rather than take out Reece, who’s in his sight, Harkness — who also took a shot to the leg from Flyte — calls it a day and heads back into the safe house for a drink. He gets about two seconds of peace before River — who’s been tearing the safe house to shreds, scrappily fighting Jane — rolls down the stairs holding his weapon of choice: a table lamp. As Jane follows on foot, Harkness shoots and kills her, then casually offers River a drink. The two share a borderline touching moment, where River finally asks, “Can you not just have been a normal dad? Anything, really, maybe just not a contract killer?” He holds a gun to his father as an MI5 helicopter lands on the property, but after Harkness encourages River to “look at what granddad got up to,” he lets his zaddy walk.

As planned, Taverner heads to the Home Secretary’s office to report treason, but she takes down “poisonous little toad” Peter Judd and walks away unscathed. Following the bloodbath, the Slow Horses — including Louisa, still recovering from her gunshot — meet at their usual spot to take shots (except for a still sober Standish) and honor their fallen joes, especially Coe. Before River leaves, Standish tells him his grandad’s neighbor noticed a light on in his house for a few days. Before she finishes explaining, River understands, hops in the car, and drives to David’s house, where a single light is on upstairs, a nod to Sid’s promise that she’d leave the light on for him like his grandad used to. (SOBBING!)

River sees Sid upstairs and hears the shower running when he enters. As Nick Drake’s “One Of These Things First” plays, he races to make tea, moves the crowbar he left on the counter earlier, and decides to pop open a bottle of wine. As River tries to arrange the glasses, light a candle, and pop the cork, his right hand noticeably bothers him. He starts panting, gasping for air, wheezing. He grabs his phone and tries to call for help, but collapses before he’s able to. The final shot of Season 6 is his still boot on the ground. And after a Season 7 preview promptly makes reference to River’s death and offers zero glimpses of Jack Lowden, we’re left to wonder: Is River dead?

What Happened To River Cartwright At The End Of Slow Horses Season 6? Is River Dead In Slow Horses?

While we’ll have to wait and see which path Slow Horses takes, thanks to the books, we know that a Russian nerve agent poisoned River. As Taverner confirmed earlier in the season, “We responded to nerve attacks on British soil with an action in Russia.” And from the looks of the finale’s final minutes, the nerve agent transferred onto River’s right hand when he grabbed the crowbar, which suggests Jim or Jane may have planted it.

How David’s house was hit, and whether the poison was meant for River, Sid, or both, remains unclear. The big question now is: Does River die in the Slow Horses books? If you don’t want to know, stop reading now.

Does River Die In The Slow Horses Books?

As always, storylines can change in text-to-screen adaptations. So who knows! But what we do know is that in Book 8, Bad Actors, River survives being poisoned! So we’re hoping the same happens in the show! We’ll have to wait and see what Season 7 has in store, but here’s everything we know about the Slow Horses season ahead.

Slow Horses Season 6 is now streaming on Apple TV.