Who was the father of Erin's baby?
To recap, last episode we saw Erin McMenamin's uncle Billy Ross seemingly confess to murdering his niece, with hints that at a family retreat years prior, Billy and Erin had engaged in an affair that saw Erin fall pregnant with DJ.
If you cast your mind back to the end of episode six, we see Chief Carter presented with a photo that was hidden in Erin McMenamin's diaries (and was rescued by her best friend, Jess). His reaction is one of shock and urgency - he demands someone get hold of Mare immediately.
As we now know, the image contained a photo of Erin and John in bed together, exposing their affair. We realise that John is actually the father of Erin's baby, not his brother Billy. At the same time we come to this realisation, Mare is approaching both the men at a fishing spot. They have an altercation involving the gun, but Mare is able to wrestle it from John's hands before any harm is caused.
Later on, John confesses to murdering Erin after growing concerned that she would reveal their affair. It seems very early on in the finale to have everything tied up so neatly, and we soon find out that the case is nowhere near closed.
Who killed Erin Mcmenamin?
This one will probably shock you, but as we've previously hypothesised, Ryan Ross was actually Erin's killer, not his father, John. The theory that Ryan was the murderer actually originated on Reddit, from user Judochopjames. They posted a popular theory that Ryan, John and Laurie's son, is connected to the murder of Erin McMenamin. And, as it turns out, he was.
Essentially, Ryan caught on to the fact that his father was having an affair with Erin. He claims he confronted his father about it, who assured him that it was over, but after reading text messages between the pair, he realised it wasn't.
He stole a gun from Mr Carroll's house, and headed to the park where he knew Erin and his father were meeting. After watching them argue, he confronts Erin with the gun, ordering her to stay away from his family. The two children wrestle, with Ryan accidentally shooting Erin in the process. He proceeds to shoot her again, before dragging her body away. Shocking, right?
After all that, it turns out his father was merely taking the fall for for him. Even more shocking still, his mother Lori (and Mare's best friend), knew the whole time. She was prepared to lie to Mare in order to protect her son, but in the end, it wasn't enough.
If you're wondering how Mare figured out that it was Ryan, it turns out he mows the lawns for Mr Carroll, meaning he had access to the shed where the gun was kept. After arriving at his school (and seeing him bolt over the fence), her suspicions were confirmed. She arrives at his house to arrest him, finding him sobbing in the arms of his mother, Lori. It's an emotional scene to say the least.
Is there a 'Mare of Easttown' 2?
As of right now, we really don't know. There's certainly a lot of open-ended questions and unresolved issues for a handful of characters, and it would be nice to see them work through these in another season.
For now, all we can do is sit tight and put our trust in the hands of Kate Winslet!