Spoilers for the Sharp Objects finale follow below. You’ve been warned.

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HBO’s excellent miniseries adaptation of Gillian Flynn’s Sharp Objects has at last come to an end, but not without one last surprise. Fans of the series have been wondering who committed the murders in Wind Gap for eight episodes now, and as the Sharp Objects finale came to a close, it appeared as though the show had settled on an unlikely killer: Camille’s (Amy Adams) mother Adora (Patricia Clarkson). But if you didn’t watch through the entire credits, you missed a crucial plot detail regarding the true killer.

Indeed, the finale confirmed what Detective Willis (Chris Messina) previously discovered, that Adora suffers from Munchausen syndrome by proxy. This disease means that Adora thrives off the attention gained from tending to sick people, and to that end she’s been poisoning Amma (Eliza Scanlen). Moreover, Adora’s poisoning goes way back, and got out of hand with Marian (Lulu Wilson), which led to her death. Camille’s resistance to Adora’s medicine from a young age is one of the reasons her mother has held such resentment for this particular daughter.

The bulk of the Sharp Objects finale found Camille finally succumbing to her mother’s “medicine” in an effort to allow Amma to escape and call the cops, but we soon learn that Amma never actually ran away, claiming she was too weak to do so. Adora laid the medicine on thick with Camille, which seemed to suggest she actually was trying to kill her least favorite daughter. But luckily Camille’s editor Frank (Miguel Sandoval) arrived just in the nick of time as the police—led by Richard—arrested Adora not just for the poisonings, but also for the murders of Ann and Natalie after discovering the pliers used to pull out their teeth in Adora’s kitchen.

But this didn’t really make a whole lot of sense. Adora couldn’t possibly have pulled those teeth out herself, and while she certainly milked the grief over Ann and Natalie for all it was worth, straight-up murder—and especially displaying the bodies—didn’t seem like Adora’s style. Perhaps Alan (Henry Czerny) gave a helping hand. But still, as the finale moved forward in time and followed Camille and Amma moving to St. Louis together, something didn’t feel quite right.

And indeed it wasn’t. In the episode’s final moments, as we learned that Amma’s new friend is potentially missing, we watched Camille going through Amma’s dollhouse only to discover that the ivory floor is made of human teeth. Camille is holding up one of the teeth in horror when Amma enters the room. At first Amma looks concerned, then her disposition quickly shifts to a sort of pride, and she delivers the gutting final line of the series, “Don’t tell Momma.” Adora's doing time for Amma's grisly crime. Cut to credits. The end.

Except director Jean-Marc Vallée had one more surprise up his sleeve, and if you didn’t watch through the credits, you missed a crucial piece of info. During a Sharp Objects finale credits scene, we saw flashes of the murders and learned that Amma didn’t act alone. It’s incredibly fast and hard to make out much, but we absolutely see that Amma and her roller skating friends definitely killed Ann together, as the others held her down while Amma strangled her. We also saw Natalie’s murder in John’s room (explaining the blood that implicated John), and although we didn’t get a look at the perpetrators, we can assume Amma’s friends helped out there too. The final flash is of Amma murdering her new friend in St. Louis, alone and full of rage and fire. That little monster.

This recontextualizes the ending and positions Amma not as a lone sociopath, but the leader of a pack of sociopaths so to speak. And book spoilers here but, in Flynn’s source material, this is the same ending—Amma killed Ann and Natalie with the help of her friends. They even lured Ann to a “party” in a golf cart before killing her, and held Natalie hostage in a carriage house for two days before finally killing her, tending to her in a very Adora-like way. The final murder is a bit different though—in the book it’s in Chicago, not St. Louis, and it lets the reveal linger a bit more, with Camille theorizing that Amma killed the girls because Adora paid attention to them.

Vallée’s choice of ending is killer (pun intended), and while it’s a bit odd to somewhat hide that crucial information in the credits, concluding the story on Amma’s final line is kind of too good to resist. But if you didn’t watch the Sharp Objects credits, then you missed the reveal that Amma had help. And even if you did, you may have been a bit confused as to what, exactly, was being shown there.

So there you have it: Amma and her friends were the true killers all along, and even outside of Wind Gap Amma hasn’t lost her taste for blood. She’s a bona fide sociopath. A fittingly wild ending to a crazy, wholly engrossing ride.