This article contains spoilers from the series finale of Mare of Easttown. After a season of devastating twists and turns, Mare of Easttown came to an end on Sunday night. Viewers were so invested in the series that they crashed HBO Max, but as soon as the app service was back online, fans finally got some answers after all of their theories. At the beginning of the episode, it was revealed that John Ross was indeed the father of Erin McMenamin's child. After a struggle in the woods, he attempted to murder his brother Billy in order to stage his death as a suicide and frame him for the murder. Mare arrives in time to intervene, and John confesses.
While the case seemed closed, some of the details simply didn't add up. While John admitted that he and Erin had been in a relationship, there were things about the night of her murder that he couldn't account for. He couldn't say what kind of gun he used to shoot Erin, and Frank swore that John seemed fine when he brought him home from the party that night after he allegedly killed Erin.
As it turns out, it was not so cut and dry after all. John's son Ryan was in fact the killer, proving Vanity Fair writer Joanna Robinson's theory correct. Stealing a gun from one of the homes where he did yard work, the troubled 13-year-old was in fact the one who shot Erin and John was taking the fall for his son. Ryan knew about John's relationship with Erin and when he confronted his father, he promised that he would end it. However, when he found out that his father had not broken it off, Ryan went to threaten Erin with the stolen gun. Ryan only intended to scare Erin off, but accidentally shot her instead.
John and Billy ended up hiding Erin's body, and when Lori found out that her son was the killer, she also hid the truth from Mare. Ryan's arrest leads to a confrontation between Mare and Lori, with Lori blaming Mare, asking why she "couldn't just leave it alone." Instead of blaming the men in her life who committed these horrible crimes, Lori instead turns on Mare. However, the final moments of the episode seem to point that the former best friends might be able to reconcile despite everything that had occurred, with a bereft Lori collapsing into an understanding of Mare's arms. It was a devastating conclusion to the case and a fitting ending to the twisty series. Kate Winslet better begin practicing her Emmy acceptance speech now.