‘Mare of Easttown’ Predictions: Who Killed Erin Top Fan Theories

Mare of Easttown Episode 6 ended with a humdinger of a cliffhanger. Mare (Kate Winslet) is on her way to confront the person she thinks is the killer — Billy Ross (Robbie Tann) — but Chief Carter (John Douglas Thompson) receives news from Jess (Ruby Cruz) that seems to blow that theory apart. Sure, Billy admitted to murdering Erin (Cailee Spaeny) in last week’s episode…or did he? What could possibly be in the photo that Jess saved from Erin’s journals that change the Chief’s mind? And what final dark twist is awaiting Mare in the Mare of Easttown Series Finale?

Confession time: I haven’t really been doing all that much theorizing about Erin’s murderer while watching Mare of Easttown on HBO. My joy comes from sitting back and watching some tremendous prestige hoagy-mouth acting. That said, I’m no stranger to the crime drama genre. I have a few theories bouncing around my head going into Mare of Easttown Episode 7. And Reddit has more.

The Mare of Easttown Reddit is chock full of folks doing their best to break down who killed Erin McMenamin. The theories range from understatedly clever to wildly twisty. However the most compelling theories seem to circle back to one family. The Ross family. Erin McMenamin’s father Kenny (Patrick Murney) was close with cousins John (Joe Tippett) and Billy Ross. And Mare’s lifelong best friend Lori (Julianne Nicholson) treated her husband’s cousin’s daughter — Erin — as part of the core family. But it seems that after Erin’s mother’s death, something went afoul at the Ross Family Reunion. Kenny and Lori have given Mare different accounts of what they all did, but it seems someone started an incestuous and illegal affair with a teenaged Erin. Hell, it sounds like either John or Billy raped her.

So did one of the tight-knit Rosses kill Erin to keep the girl from ruining the family with their darkest secret? And if not, how does Erin’s journals factor in? What was her ex-boyfriend Dylan Hinchey (Jack Mulhern) trying to cover up? Finally, is it possible that Mare’s family is more involved in the case than she knows?

Here are the top four theories we have about who killed Erin on Mare of Easttown, and some bonus thoughts…

The Way Too Obvious Choice for Erin’s Killer on Mare of Easttown… Billy Ross

Leading into Mare of Easttown Episode 6, it was looking more and more like Erin’s squirrelly cousin Billy was hiding something dark and nefarious. You know, like he was her killer. The evidence pointing at Billy came down in an avalanche last week. Not only did his own father see him washing bloody clothes at 4 AM the night Erin was murdered, but he seemingly confessed to killing Erin to John Ross. Mare scoops up evidence that Billy likely raped Erin and impregnated her. Later, Lori tells Mare that John told her Billy killed Erin (even though she swore to her husband to keep this information from Mare).

So, Billy killed Erin, huh? He was ready to confess at the station and everything. He even has a gun in a tackle box.

Well, as Decider laid out immediately following Mare of Easttown Episode 6, Billy Ross is way too obvious a choice. Furthermore, we didn’t hear the entirety of Billy and John’s conversation. Billy only admits to the murder after John coaches him into it. Finally, something that Jess took from Erin’s journals makes it imperative for the Chief to reach Mare before she apprehends Billy.

We’re going out on a limb and saying that because Billy is the most likely suspect, he’s probably the show’s final big red herring. Which leaves, the next most likely suspect…

All Signs Point to…John Ross Being the Killer on Mare of Easttown

John Ross has a talent for infidelity and a knack for lying. His “alibi” was getting drunk with Mare’s ex Frank (David Denham), which could be a saved photo from an earlier time. So that could be bunk. Furthermore, it could have been either Ross brother who raped Erin at the family reunion. All Mare has is a receipt for the girl’s locket that was paid for by a “Ross.” She jumps to the conclusion that it’s Billy, but it could just as easily have been John.

If you look at Reddit, there’s a conversation started in a reaction post to Mare of Easttown Episode 6 that speculates that Billy was drunk and doesn’t remember helping John kill Erin or that John is making Billy take the fall. That would be why Billy was seen cleaning the bloody clothes at his father’s house — so John wouldn’t take them home to Lori and the kids — and why John tells Lori about Billy’s “confession.” He knows she won’t lie to Mare and is hoping to build a case framing his weaker younger brother.

Of course, if John is the one who raped and impregnated Erin, he’s not the only one with a motive to kill the girl. Or a means to manipulate Mare’s investigation…

The Most Likely Mare of Easttown Twist…Lori Ross is Erin’s Killer

So you want a twist ending, folks? The most compelling one isn’t Frank Sheehan or the turtle or even Dylan Hinchey after all. It’s Lori Ross.

There’s a bunch of theories on Reddit that lay out why Lori would kill the girl who may have threatened to destroy her family (and why Billy would help cover it up). Some of them even point out that the body is staged to look like a rape and murder, but Erin wasn’t sexually assaulted. It could be a feint from a female killer to make the cops assume a man did the deed. After all, Colin Zabel (Evan Peters) has to correct Mare’s own bias when he tells her that a man or woman may have killed Erin.

Lori has the motive and she also has the biggest boon for a killer in Easttown: Mare trusts her completely. If there’s going to be a massive swerve in the Mare of Easttown series finale, I would bet that it’s the reveal that the killer is the only person Mare trusts. Or one of these bonkers theories…

A Quick Rundown of All the Major Remaining Mare of Easttown Theories…from Siobhan Sheehan to Ryan Ross and Everyone in Between…

So yeah, there are a lot of theories bouncing around these interwebs. Some possible suspects to consider (or not)…

• Dylan Hinchey, as his alibi went up in smoke and he burned Erin’s journals. However, the most compelling Dylan theories out there (in my opinion) frame him as a drug-dealer desperate for Mare not to learn the extent of his business. Perhaps he was Kevin’s supplier?
• Ryan Ross, as the child is a Ross and has shown violent tendencies. Is it possible the secret he and dad share is the truth that he killed Erin?
• Frank Sheehan, because why else would a seemingly nice family man and high school teacher help a student in need out, huh?
• Siobhan Sheehan, because Mare’s father had a gun like the murder weapon. Oh, and there’s this theory that the photo Jess has shows Erin with Kevin. This ties back to several other theories with the implication that her baby is also Mare’s grandson.
• Richard Ryan (Guy Pearce), because why else cast Guy Pearce? Except to be the hot love interest of a movie star? His alibi is sleeping with Mare, so I think we’re okay? (And if betrays Mare at all it will be stealing her story for a book. After all, Mare of Easttown’s writer and creator Brad Inglesby’s wife is from DelCo.)
• Deacon Mark…uh…because he’s there…and got rid of Erin’s bike.
• Mare Sheehan herself. Why? Because wouldn’t that be stupid wild? Or just stupid?

Mare of Easttown Episode 7 will premiere on HBO and HBO Max on Sunday, May 31 at 10 PM ET. 

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