Mare of Easttown Theories: Who Killed Erin McMenamin?


I stand by my opinion that there are too many detective dramas. There are far too many more detective dramas dealing specifically with the gruesome deaths of young women. Yes, the new, Kate Winslet-led drama on HBO Max, Mare of Easttown, is one of these dramas. And yet, unlike so many other tired tales of borderline alcoholic cops and brutalized teenagers, it harnesses the stereotype to tell a bolder, smarter story, rather than regurgitating the same police propaganda we’ve had forced down our throats for decades.

To be clear, the audience is supposed to believe that, yes, deep down, Mare is a good cop. We just can’t be positive she’s a good person.

In Easttown, Pennsylvania, Mare (Winslet) is a bone-tired police detective who believes herself to be an excellent cop. So the fact that she has yet to find a missing young woman named Katie Bailey (Caitlin Houlahan) galls her, especially when you consider that Katie is the daughter of Dawn, Mare’s former friend and high school basketball teammate. As Mare circles around a whole lot of nothing, she continues to spiral from the sudden loss of her son, Kevin (Cody Kostro); the creeping rot of poverty and the opioid epidemic inside her own community; and the impending nuptials of her ex-husband Frank (David Denman). She’s also living in the same house with her mother (Jean Smart) while raising a high school-aged daughter, Siobhan (Angourie Rice), and her late son’s own young son.

kate winslet as mare sheehan in mare of easttown


Meanwhile, teenager Erin McMenamin (Cailee Spaeny) is doing everything in her power to keep hope alive while raising her infant son. She lives with her verbally abusive father, Kenny (Patrick Murney), and attempts to co-parent with her ex-boyfriend, Dylan (Jack Mulhern), who is openly dismissive and cruel. Yet Erin, in all her exhaustion, remains optimistic, prepping for a date night at a party near the woods. But when she arrives, she realizes she’s been catfished by Dylan’s new girlfriend, Brianna (Mackenzie Lansing), who ferociously attacks Erin out of jealousy and spite. Despite Siobhan’s protests, an injured Erin ventures alone into the forest, where she is discovered, dead, the next morning.

Mare of Easttown is about who killed Erin MeMenamin. It is also about why that matters, and why our perceptions of who is evil are often so fundamentally flawed. It’s a fantastic show, but to glean the true meaning from it, we have to start with Erin—and what exactly happened that night in the woods.

Who killed Erin McMenamin?

By the end of episode 3, which aired Sunday, May 2, a few suspects revealed themselves. But that doesn’t mean we’ve found the culprit yet. Let’s break them down.

still of erin mcmenamin and kenny mcmenamin in hbo's mare of easttown


Kenny McMenamin

First, there’s Kenny, Erin’s dad. His track record isn’t exactly glowing when it comes to Father of the Year nominations. He hollers at his daughter after burning his mouth on the plate of food she heated up for him. He makes her do most of the work around the house. He demands she borrow money for her son’s ear surgery from Dylan—Kenny refuses to pay for his daughter’s “mistake” anymore. And he clearly knows nothing about the mystery boy Erin wants to meet up with that night, as she hides her texts from her father and sneaks out when he’s not watching.

But fumbling fatherhood isn’t an indictment for murder, especially of your own kin. The chance that Kenny himself ventured into the woods, stripped his daughter of her clothes, and killed her with a blunt object seems too abhorrent to consider. But Mare of Easttown does a good job of giving you solid reasons to suspect anyone and everyone, without using the trope as a crutch. Kenny very well could be involved, even if indirectly.

In episode 2, we watch Mare drive up to Kenny’s place and deliver the news of Erin’s death. At this point, my suspicions of Kenny’s involvement all but dissolved—his pain is so visceral it seems to reach through the screen and choke you. In the wake of his grief, he jabs a figurative finger at Dylan, claiming the teenager “hated” Erin for giving birth to DJ.

Of course, Kenny has to complicate things further by tracking Dylan down and shooting him. Dylan survives, as we see in episode 3, but Kenny’s rage gives us reason to believe he’s lacking in the mental stability department. Oh, and he’s the only one on the suspect list with a registered firearm—a key detail, as Mare and Detective Colin Zabel (Evan Peters) discover Erin’s finger was blown off by a bullet.

jack mulhern as dylan in hbo's mare of easttown


Dylan Hinchey

But Kenny’s itching trigger finger doesn’t let Baby Daddy off the hook. At the top of the suspects list is still Dylan, or Brianna, or some combination of Dylan and Brianna. We already know Brianna is capable of terrible violence: She was the one who forced Erin to run into the forest in the first place. She’s vicious and unafraid to show it, but kids are nasty, especially when they feel threatened, and cruelty, again, doesn’t necessarily beget murder.

So what about Dylan? He stood and watched his new girlfriend beat up his ex and didn’t do a thing to stop it. He clearly resented Erin for keeping their baby and expecting him to pay for that baby’s livelihood. Who knows, maybe he figured his waning teenage years would be better off without a responsible mother for his sick child? But, if that were the case, why draw attention to himself and Brianna with Erin’s (very public) beating? It was on camera! If he really wanted a quick and quiet murder, it makes no sense to create a crime scene right beforehand.

In episode 2, he’s taken in for investigation, and Mare grills him to force a confession. “If you’re lying to me, it’s going to be very bad for you,” she threatens (convincingly, I might add). And yet he does lie. He lies about watching Erin walk into the woods, and he lies about his relationship status with Brianna. He’s very cavalier about the whole thing, and yet he doesn’t stink of guilt, either. More than anything, he reeks of exasperation. That doesn’t clear his name, but it does make the case less straightforward than Mare would prefer.


Frank Sheehan

In the final seconds of episode 2, Erin’s best friend, Jess, has her own confession to make: Apparently, Erin had a relationship with one Frank Sheehan, Mare’s ex-husband. And Jess seems to think he’s DJ’s father. (Jerry Springer, are you listening?)

If that’s the case, then Mare might be cuffing the man she once married. If he’s DJ’s dad, there’s a motive for him to kill Erin, especially as he embarks on a new journey toward marital bliss with his fianceé, Faye. If Mare of Easttown wants anything out of its audience, it’s for us to constantly question who we know, who we trust, and who we consider “good.” And that extends to gentle, good-humored Frank.

evan peters and james mcardle in hbo's mare of easttown


Deacon Mark

I have to be honest—I don’t like this theory, and not because it doesn’t have legs. It’s because it has a whole millipede’s worth of legs, and that just seems too simple.

We learn in episode 3 that the last person Erin called the night she died was Deacon Mark (James McArdle), a quiet, austere spiritual mentor who practically seeps Bad Guy vibes. To make things even more obvious, he’s got a mark on his record—Zabel gets a tip that the holy man might not be so holy after all, though the particulars of his prior behavior are still a bit murky. Finally, Mare of Easttown packages up our neat little suspicion sandwich with a dollop of condemning evidence: In episode 3, we watch Deacon Mark retrieve Erin’s bike from the back seat of his car and throw it into the river.

It’s a classic story of sin: The religious leader caught in the act with an innocent child and his desperate attempt to cover it up, through extortion or bribery or worse. Of course the deacon is the murderer. Aren’t all men of God secretly demons in disguise?

Look, we’ve all been given more than enough reason not to trust men in holy uniform. Even as someone who attends church every week, I can admit this is true. But making Deacon Mark the murderer—and giving us this much evidence after only three episodes—would mean Mare of Easttown isn’t as smart of a show as I believe it to be.

Remember, this show wants us to second-guess our assessment of good and evil. Like Mare, we’re supposed to wonder who really deserves saving (including ourselves), and whether “deserving” even matters in the first place. So making Deacon Mark into a flashing-neon-sign-level Bad Guy doesn’t add up.

So I’d be willing to bet there’s more to the deacon’s story, and that we’re still looking for someone entirely different, perhaps someone connected to the still-missing Katie Bailey. But that doesn’t mean the perp won’t be hiding in plain sight.

angourie rice in hbo's mare of easttown


Siobhan Sheehan

This theory, on the other hand, I love. I’m not sure if all its pieces fit together, but wouldn’t it be fun if they did?

Of the suspects in this article, by far the most popular option among the show’s fans in one Reddit poll is Mare’s daughter, Siobhan. And there’s at least some reason to suspect her involvement in Erin’s murder. She is, after all, the last person we see with Erin on the night she dies. She rescues Erin from Dylan and Brianna’s pile-on, only pausing after Erin shrugs her off and walks into the woods. Plus, Siobhan didn’t tell her mother about seeing Erin on the night she died—at least, not until Mare tracks her down and drags the information out of her. It’s all a wee bit suspicious.

“The reason I’m sus on Siobhan is that we have no idea where she was after, didn’t pick up her phone all day, and all her buddies came forward while she was mia,” wrote one Reddit user. That’s not exactly strong enough for an arrest warrant, but wouldn’t it be fascinating to see Mare’s golden child pegged for this crime, even if she didn’t do it?

joe tippett and robbie tann as john and billy ross in hbo's mare of easttown


John and/or Billy Ross

An excellent theory on Reddit points to the potential involvement of the Ross boys, friends of Frank Sheehan and family of Lori Ross, Mare’s best friend. The two of them were out drinking with Frank the night of Erin’s murder, and they drove Frank home around 2 a.m., which means they were out and around (and drunk) during the time Erin was wandering beyond the woods. And when they break the news of Erin’s death to Kenny, there’s something…off about their behavior.

“Pay close attention to Billy Ross,” the post reads. “Something about his body language seems off. Could be nothing, but I definitely got the impression of feelings of guilt more so than sorrow. In fact, pay close attention to Billy Ross in any scene he’s in. His body language just seems off, but he’s such a background character for now that you don’t really catch unless you’re actively paying attention.”

More evidence that, to suss out the true murderer, Mare of Easttown expects you to suspect everyone. That’s part of what makes the ride so fun.

Watch Mare of Easttown on HBO Max

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