Mare of Easttown ending explained: Who really killed Erin?

Warning: The following article contains spoilers for the Mare of Easttown ending.

Well, tonight was the series finale of Mare of Easttown and we finally know who killed Erin. Hopefully, you were able to watch. The answer might not be who you anticipate, either. The beginning of the episode takes us to the fishing cabin where John and Billy are as Mare rushes to catch up.

We find out that the photo showed John and Erin together, as opposed to Erin and Billy. At the cabin, John pulls out the gun from the tackle box and tries to kill his brother, intending to set him up for the entire thing. Mare gets there in time to intervene and John ultimately takes the fall for the murder. He confesses to killing Erin, and it looks like that’s the end of it.

The episode continues, slowly wrapping up plotlines like Siobhan going to Berklee in Boston, Carrie going to rehab again (thus giving Mare custody of Drew) and Frank and Faye getting married. But you get the feeling that another shoe is waiting to drop. That’s when Mare gets a call from Mr. Carroll.

Mare of Easttown ending explained: John confessed to protect someone in his own family.

Mr. Carroll tells Mare that the night Betty first called her, back in the series premiere, when the whole prowler debacle happened, some items went missing around the house. One of those items was his Colt Detective Special gun, the same gun used to kill Erin. But not long after it went missing, the person who took it returned it. The only person with access to the Carroll’s shed, apart from them, was the kid who cuts their grass: Ryan Ross.

Mare quickly realizes what happened. Ryan found out that John was having an affair with Erin thanks to text messages on his phone. That’s why John forced him to keep it a secret from his mom. While Lori assumed John was sleeping with Sandra again at the time, John later told her everything and convinced her to lie to Mare and pin the entire thing on Billy.

The night Erin died, Ryan stole Mr. Carroll’s gun and went to see Erin at Brandywine Park (using his dad’s texts to find out where she would be). He only meant to scare her with the gun, hoping she would leave his family alone, but Erin tried to grab it and they fought over it. Ryan accidentally shot and killed her.

Then John and Billy came in and took care of her body while Ryan hid the gun back in the same place he originally found it, the Carroll’s shed. Mare is forced to arrest Ryan, which devastates Lori. She blames Mare for the fact she no longer has a family, even though it’s really John’s fault.

And I know Ryan is a kid, but I can only spare him so much sympathy. I mean a teen girl was murdered, taken advantage of, and then had her body stripped half-naked and abandoned in a river. The Ross family decimated her life. That poor girl went through hell from beginning to end from every person in her life.

The entire season of Mare of Easttown is now streaming on HBO Max.