'The Sinner' Season 2: Heather and Marin's story-within-a-story lays out the clues
Probably why Julian killed his parents is not yet known, but it is clear that he certainly is not Vera's son but somebody more unapparent.
Heather and Marin are not just two separate characters in 'The Sinner' who can be passed off as bystanders. Their story might just be as important as Julian's own. The subtlety of the second season lies in the fact that it has managed to weave one story within another without distorting the design. Season 2 began with the question of why would a 13-year-old boy kill his parents. However, pretty soon into the first two episodes, it was clear that this season is not just about that one question.
Episodes 1 and 2 surely have set the pace for the murder mystery to slowly unravel itself while covering up the gloomy past of Detective Harry Ambrose. However, by the third episode, it seems that 'The Sinner' has diverted its audience towards another equally important pair of characters: Detective Heather Novack ( played by Natalie Paul) and her school sweetheart, Marin (played by Hannah Gross). While talking about her relationship with Marin and how it has helped Heather grow, Paul said, "Incidences from my high school years and my teenage years with my best friend reveal more about how Heather got to be who she is...We were trying to figure out the 'why' of the case, but you also see more about the 'why' of the detectives."
Episode 3 opens up with Ambrose telling Heather, "When a boy that young kills it's never just his fault", while they sit at a cafe where the incident at the motel is being reported on television. Ambrose directs Heather to the fact that "it is not the time to stop asking questions" and mentions Marin, who too was a part of the commune and had disappeared almost 10 years ago. While Ambrose insists Heather open up about the incident, she seems reluctant to speak about it, dismissing it as a "lost cause". However, a visit to Marin's house and after having a word with her mother, Heather realizes that there was a bigger story behind Marin's disappearance.
Episode 2 saw Marin getting inside the barn along with one of the members of Mosswood, and in the present episode, she returns home to tell Heather about her experience. Although the scene only projects a flash into Heather's memory, it holds a very strong ground in the show. Marin has just visited the commune and she is absolutely overcome by what she experienced there. As Hannah Gross had mentioned during an interview that her character is someone who is trying to break free and get into something new, it is justified to see Marin so smitten by something which is otherwise considered a "cult" by most.
Marin's excitement is just as innocent as Julian's ignorance. Both the characters seem to be placed parallel to each other in different periods in time, and both have been the victims of the workings of Mosswood. Just like Julian is trying his best to abide by Vera's words and not disappoint her, Marin will probably slowly get into the pattern of abiding by everything that the commune stands for. Marian and Julian are a part of that portion of the spectrum which has been affected directly. Ambrose and Heather stand on the other end which has been passively traumatized with the workings of it.
While it is not yet clear if Ambrose's mother too was a part of the commune, but a few flashbacks show him witnessing his mother's gradual descent into madness. Heather, on the other hand, too had a first-hand experience in her loved one's madness. Although madness would be an exaggerated term to use; but, what Marin was doing in her reckless moments were nothing less than insanity. She steals away from her family and friends and eventually disappears into the world never to be found again. Both Heather and Ambrose have lost a loved one, and each has been helpless in their own times to do anything about it.
But Heather has received a second chance, and this time probably she will find answers to questions that she never even asked. One significant clue that Episode 3 has left us with is if Julian is Marin's son. When Heather visits Marin's mother, she receives a box full of Marin's belongings. As she examines it in her room, she discovers a book titled 'Dolphin Beach' by Caitlin Roche. As she flips through the pages she notices that the name "Julian" has been circled in the books a number of times. It immediately strikes her that there was a big possibility that Julian was actually Marin's son.
The investigation begins as soon as she informs Ambrose about it, and they arrange a meeting with Dr. Sheldon Poole who was apparently present when Julian was born. However, when he spills the fact that he did not see anyone giving birth, he immediately kills himself and that in a way hints at the fact that Julian is certainly not Vera's son. They also discover a small replica of the stone figure which Heather had seen at Mosswood, inside Poole's storeroom. With all the clues hinting at the possibility of Marin being Julian's mother, the pieces in the puzzle might finally seem to come together.
Although it's still not known what led those two young individuals to commit such dire acts. As showrunner Derek Simonds had told Variety the story is actually weaved around Marin. "It’s actually [Marin’s] narrative and what happened to her that all of the other character perspectives are revealing. That’s the mosaic that is coming together." He also referred to the fact that putting the women characters as a lead has actually helped frame the true turmoil of the show: empowerment. "The sexual politics between men and women — the way that women struggle for power and self-actualization in today’s culture — that really resonated with audiences and with us as storytellers [in season 1], and we wanted to explore that again."