So my theory is that Celeste and Perry's relationship is going to culminate at trivia night with one of them dying after falling down the steps. I think Jane is going to see Perry and identify him as 'Saxon Banks' which will lead to a heated argument between Celeste and Perry, putting their violent relationship out in the open for all to see. And one of them is going to shove the other and cause the other's death.

I'm not totally sure which one is going to die though. The tragic ending would be Celeste dying after Perry (presumably accidentally) pushes her down the stairs. This theory is supported by the statistic that non-fatal strangulation is a major factor leading to homicide or attempted homicide, and so Perry killing Celeste would fit with the domestic violence arc.

On the flip side I could see Celeste standing up for Jane and eventually pushing Perry, accidentally causing him to fall down the stairs and die. This might be considered more of a "happy" ending, and I'm kind of leaning that way when I consider what's going to happen. It would certainly provide a bit more closure when the show concludes versus Celeste dying.

I'm also almost 99% sure the twins are going to turn out to be Amabella's attacker(s). I was kind of thinking it could be Chloe, but I think that's too much drama for a show that's going to wrap up in 7 episodes. The twins being the bully (or bullies) is easy to explain, fits with what we've seen, and could contribute to the eventual climax between Celeste and Perry.

But now that I say that, maybe Renata is going to step in to the argument between Celeste and Perry and Renata will be the one to push Perry down the stairs in retribution for what happened to her daughter? That might happen, but I still think less likely than Celeste or Perry being the "culprit" so to speak.