'Mare of Easttown' Finale: Who Is the Killer? Who Fathered Erin's Baby?

This article contains spoilers for the first six episodes of Mare of Easttown.

As Mare of Easttown comes to what is sure to be a devastating and quietly desperate conclusion tonight, fans are spending the last few hours before the show airs to solidify their theories for the show's two central mysteries: who killed Erin McMenamin and who is the father of her baby, DJ? Depending on your theory, this could be the same person or two different people, so let's run down some of the most popular speculations ahead of the finale.

DJ's parentage is the key to the mystery of the killer in this interlocking puzzle of pain. After a DNA test proved that Dylan was not the boy's actual father, most men in Erin's life immediately looked suspicious. Her second cousins Billy and John Ross are the two most likely candidates, and Mare seems to believe that Billy is both the father of Erin's baby and her killer. However, John's suspicious activity -- What's on the photograph? Whose gun is that? -- casts some serious doubt on Billy's guilt.

Members of Mare's own family are also candidates for potential fathers as well. While Mare's ex-husband Frank was originally the subject of a rumor that he was DJ's father but was cleared by a paternity test. However, there is a theory that Mare and Frank's son, Kevin, was also in a relationship with Erin before he died and that he is DJ's father. This would also explain why Frank was seen giving Erin items for the baby.

The identity of the baby's father plays directly into who could be Erin's killer. If the baby is John's, he is an obvious choice, but members of his family also get cast with suspicion. John's wife Lori, Mare's best friend, becomes a suspect if her husband fathered a child with someone else. Additionally, their troubled son Ryan is at the center of another theory. Could Ryan's decision to murder Erin be the real secret that John told him to cover-up?

Additionally, something about Dylan doesn't add up. He clearly had some rage against Erin before her death, especially regarding the money that she needed for DJ's surgery, and he was missing for a few hours during the night she was killed. What is he working so hard to keep from Mare by burning Erin's diaries? On top of all of this suspicious behavior, viewers also have to consider the Guy Pearce of it all. Is the writer simply new in town or is there a more sinister link? Would HBO really have cast such a big name just to be Mare's sometimes lover? Fans will soon have answers, but will they be the ones that they want?