A BLL fan, who goes by the username emmyego, has put together a compelling theory suggesting that Corey - yes, Jane's boyfriend who may or may not be an undercover cop - is actually Perry's brother. She writes that she has read all of Liane Moriarty's other books and thinks this plot twist is right up the author's alley.
"Having mentioned the 'deceased' brother many times (subtly) throughout the season, and it’s clearly playing a role in the season finale, it is very likely that this aspect of Perry’s life will be used as the final plot twist. No one seems to suspect it so far, which is true to Moriarty’s style," she writes on the post.
"When looking at the main changes between season 1 and 2, the introduction of Corey and the prominence of Perry’s past (hence the introduction of Mary-Louise and mention of his brother) seem to stand out the most. It would make sense that these are connected," the post continues.
"Alexander Skarsgård mentioned in an interview that we will receive a further insight into Perry’s childhood and why he turned out to be so violent. This kind of disproves the ‘he killed his brother’ theory because that would mean he had to be violent from the get-go. Instead, it’s highly likely that there was some sort of trauma inflicted upon Perry, and it’s not too far-fetched to believe that Mary-Louise had a motive to fake her other son’s death. There could be a myriad of logical explanations for this (of which we know Celeste starts to ‘question.’)"
You still with us? Because there's more:
"Some were saying that Corey is there merely as a love interest for Jane. While this may be true, Season 1 ended with Jane taking Tom (the coffee shop guy) to the Gala. Why not just keep Tom as the love interest? This further eludes that Corey’s character has more significance than once thought.
Also to keep in mind- the way that the ’Perry was Jane’s rapist’ plot twist was so effective is because Jane and Perry were never introduced to each other in present time, so the audience struggled to put the two and two together. Though Corey and Mary-Louise have been a big part of Jane’s life this season, Corey and Mary-Louise have actually never been in the same scene together... Jane also has a flashback to her assault when dancing with Corey, which would make sense if they were brothers. Celeste also looks at Corey very strangely at Amabella’s party."
Admittedly, the theory is a little farfetched - what does Corey get out of starting a relationship with Jane if he really is Perry's brother? And, if the series is really about to end, surely we need a little more time to unpack this revelation?
Someone else speculated that Corey has been hired by Mary Louise to find out what happened to her son - he did react weirdly when she told him she'd been raped (he responded "really?"). Another noted that season one ended with Jane dating Tom, the coffee shop guy, so if Corey really is just a love interest, why not stick with him?
So. Many. Questions.