Mare Of Easttown Finale Predictions: Who Killed Erin McMenamin?

Kate Winslet in Mare of Easttown / HBO

Who killed Erin McMenamin? That’s the million-dollar question heading into Sunday’s series finale of HBO’s Mare of Easttown. For those who have not watched, Mare of Easttown stars Kate Winslet as Mare, a local detective tasked with solving the murder of a teenage mother in a Pennsylvania suburb outside Philadelphia.

Before we go further, this is your spoiler warning. I will be discussing spoilers so if you haven’t caught up yet or plan on watching the show at some point, stop reading. Mare of Easttown is a small-town murder mystery with an excellent leading performance from Winslet. I was hooked from the first episode. Ok, let’s move on.

*******Spoilers from here on out*********

In the penultimate episode, Billy Ross confessed to the murder of his cousin, Erin. Billy’s brother John, the adulterer (cheap shot by me?), decided to take Billy up to their father’s cabin for one last fishing trip instead of turning himself in. Is Billy aka Fredo going out in the boat?

Mare tracked down the origins of Erin’s necklace and confirmed that a Ross family member bought it. Mare raced up to the cabin to confront Billy, who she believes killed Erin. Mare has good reason to believe Billy killed Erin. Plus, Billy concealed the weapon in the tackle box of his fishing gear that potentially murdered Erin. There’s also the possibility that Billy fathered Erin’s child.

While Mare raced up to the cabin, Jess visited the precinct and turned in the photo she pulled out of Erin’s diary. Chief Carter looked distressed after viewing the photo and urged his colleague to call Mare.


So who killed Erin? Here are the suspects.



He did confess to the murder, right? Billy clearly loved and cared for Erin. There may have been some inappropriate and extracurricular activities that took place between cousins. For a show that’s had twists at the end of every episode, Billy as the murderer seems way too obvious. Do I believe he loved Erin? Yes. Is he hiding something? Yes. But did he kill Erin? No.


Mare’s best friend being the killer is a twist that would elicit a huge reaction on Twitter. On the night of Erin’s murder, Lori was at the bar with Mare celebrating the anniversary of Mare’s big shot, but her whereabouts are unknown later that night. Di Lori kill Erin? Perhaps John cheated on Lori with Erin, which led Lori to take matters into her own hands and kill Erin to save her marriage. I don’t feel Lori is the killer, but she’s hiding a major secret from Mare.

There’s a Reddit post that selected Lori as the murderer because of her Dave Matthews Band t-shirt. I want Lori to be the one who did it now.



The word I associate to describe Dylan is scummy. This dude reeks of cigarettes, alcohol, and bad decisions. I’d like to believe he was once a good kid, but good kids don’t threaten teenage girls with a gun to their head. Like most characters in Mare of Easttown, Dylan is hiding a major secret. I don’t believe Dylan killed Erin, but I’m inclined to think he knew the real identity of DJ’s father. Perhaps the Ross family paid Dylan off to keep quiet when he found out the baby was a product of incest. All I know is Dylan probably smells like shit and needs to shower more than twice a week.



Why is Guy Pearce in this show if he’s not the killer? Many believe Richard was involved with Erin’s murder because of Pearce’s involvement. Pearce is almost too big of a star to be an emotional support character with not much to do in the show. Why are we all cynics? Can’t Richard just like Mare and not have ulterior motives? If you told me Richard killed in his past life to become a better writer like Sharon Stone in Basic Instinct, you could be onto something. Richard didn’t kill Erin because he slept with Mare that night. Pearce very well might be a huge red herring.


Now we’re cooking with gas. John is my leader in the clubhouse for the one who killed Erin. For starters, he cheated on Lori so he’s willing to commit immoral acts. John was at the family reunion that Erin attended and could have purchased the necklace for his younger cousin. Why would John let Billy confess to a murder and respond with a fishing trip to the cabin? John tells more lies than a game of telephone. The way Chief looked at the photo was so shocking that it represents a “Mare has the wrong guy” moment. It has to be John… right?



Frank might have seemed like he was the “normal” one in his relationship with Mare, but he’s just as problematic and twisted as his ex-wife. Who buys a house DIRECTLY BEHIND his ex-wife’s property? Frank once helped Erin out by donating baby supplies for DJ. Maybe he spent a little too much time with Erin if you know what I mean. If we couldn’t trust Roy from The Office, why should we trust Frank?

Deacon Mark


Deacon Mark is a weird cat. He received complaints from his old parish about his involvement with kids before he was transferred to his current role. Deacon Mark saw Erin the night of her death. Those are his words, not mine. He also chucked Erin’s bike into the river. Just like Dylan, Deacon Mark is too obvious of a choice, but that doesn’t change his creepiness.


Siobhan did not kill Erin strictly because of her musical taste. I refuse to believe a fan of Boygenius and Phoebe Bridgers would kill another human.

So Who Killed Erin?

Someone had to kill Erin in Mare of Easttown. Here’s my theory:

Both John and Billy loved Erin more than a cousin. John began his affair with Erin at the family reunion. Erin then confided in Billy about her relationship with John, which upset Billy. Erin knew it would never work with John because of his marriage to Lori. Then, Lori later found out about this incestual affair but remained quiet because of the shame it would bring upon her family.

John continued his affair with Erin until she was pregnant with his child. John could not support the baby because it was a product of incest and if this secret ever went public, it would ruin his life. This is where Dylan comes in. A pregnant Erin had sex with Dylan to make it appear that Dylan was the father.

Fast forward to the events leading up to her death. After Dylan refused to pay for DJ’s ear surgery, Erin went to John to ask for money. John refused, which led to Erin’s stint as an online prostitute. After being humiliated in the woods, Erin panics and calls Deacon Mark, Billy, and John. After speaking with Deacon Mark, Erin meets up with John in the park and they have sex. Midway through, they stop and Erin begs John to pay for DJ’s surgery. John once again refuses. Erin threatens to go public with their incestuous secret. The two have an altercation which ends with John killing Erin.

Where do Dylan and Jess come in? This is the only part of my theory that lacks conviction. My gut tells me Dylan and Jess had a secret relationship. Erin eventually found out the night of the woods party. Why would they burn Erin’s journals? Once again, I’m not entirely sure, but maybe Dylan and Jess believed Erin knew about their affair for a while so they burn her journals just in case Erin wrote about it.

After John flees, Billy arrives at the scene and witnesses Erin’s dead body on the ground. Billy breaks down and hugs her, which explains the blood on his clothing later that night. Billy then panics, knowing he will be blamed for Erin’s death if someone spots him. So Billy drives Erin to the creek and leaves her there, hoping someone else will be blamed for Erin’s death.

Billy seems like a person who can be easily manipulated. After John hears about Billy and the bloody clothing, John decides to coerce Billy into confessing to the murder of Erin. Since Billy can’t take the guilt anymore, he confesses to the murder right in front of John. Mission accomplished.

However, John thinks Billy will tell the truth about his brother’s relationship with Erin and admit to not killing her when it comes time to discuss the matters with Mare and the police. John can’t take that risk so he takes Billy up to the cabin to kill him.

End Scene.

Hopefully, we all receive the answers we need on Sunday night.

What are your predictions for the Mare of Easttown finale? Leave your thoughts in the comments below or tweet us, @danny_giro.