Reddit Is Going Wild With Theories About Who Killed Erin On 'Mare Of Easttown'

Brianna is almost too obvious a suspect to be the killer, but that doesn't mean she wouldn't be a satisfying answer. Reddit fans admit they love to hate her, though most argue she's probably a red herring. That said, in the most recent poll breaking down the suspects, more than one Redditor pointed out The Undoing claimed to have a massive twist... and then it was the most obvious suspect.

There are convincing arguments to be made that Brianna is the murderer. She's a terrible person and she has a violent streak she learned at home from her father. (Her father is now stalking Mare for even thinking his daughter could have done it.)

Say it with me now: The man had her bike in his trunk.

As Reddit user harperblossom noted:

The simplest theory is that Erin called Mark asking for money for the surgery because he’s DJ's real father, and she was going to expose him. He agreed and told her to meet him in the park. Erin rode her bike there, and he drove there. When they arrived, he kills her, puts her body and bike in his car, and drives away. He later disposed of her body, cell phone, and bike.

Deacon Mark is desperately hiding something. Although, fans should note that no one knows for sure if Erin called him. All the show has confirmed was her phone called his. Perhaps Mark is covering up for someone else who called him from her phone, desperate for help with a body?

If Deacon Mark is covering up for someone, the most obvious answer is Father Dan, his boss. A lot of Redditors have honed in on the idea that the killer is someone related to Mare. That's why there's a lot of suspicion swirling around Siobhan, who is a very unlikely suspect.

But Father Dan is someone related closely enough to be in Mare's house when she gets home. He's an authority figure someone like Erin would easily trust; after all, he's a priest. More than one theory suggests this could be an entire trafficking ring, which also explains Katie's disappearance and perhaps even Mare's refusal to look into it.

Frank lying about his level of connection with Erin is a huge red flag, but it's not necessarily proof her either the father of her baby or the killer. He could be a really nice and slightly stupid guy. (Consider how he bumbled with telling Mare about his engagement and there is all the proof you need on both counts.)

That said, Frank had been acting suspiciously even before Jessie went tattling about the diaper delivery. And at least one Redditor is convinced it is him, which, according to a theory, would lead to Mare eventually adopting Erin's baby.

Then there are the Ross brothers, one of whom is the husband of Mare's BFF Lori. Redditor GringoMambi has a whole breakdown about their drunken exploits alibi:

• Frank passed out, but John and Billy didn't.
• Both are close family friends who Erin would have trusted implicitly.
• Both were surprisingly willing to go break the news to Erin's father.

Being there for Erin's father from the get-go paints a picture of supportive friends and detachment from possible involvement. Which could possibly build their case even more to convince Erin's father and the community that no way in hell it could ever be them. This scene might be harder to read as it's natural for that kind of news to come from close friends and or them to be weird about it. BUT, watching that scene, pay close attention to Billy Ross. 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.

Only time will tell if any of these theories are correct.

Mare of Easttown continues airing Sundays at 10 p.m. ET on HBO and streams on HBO Max starting the next day.