Beep. Boop.

At the end of episode 7, Dylan is apparently turning himself into the police. He also heavily implied he killed Clara. And we’re supposed to think he’s the killer, but there’s still a whole episode left and you lose any suspense for your finale if the killer is caught before the episode even begins. 

So my theory is he did kill Clara because he thought she was the killer. Then after her slept with Allison (which, ugh, I hated that plot point so much), he somehow figured out that Margot had to have been the killer (they did make a point of showing the ‘I’m Here’ note in Allison’s drawer when she was getting the condoms, so maybe that note was somehow a clue for him. But then he didn’t act on it until after having sex with “Lennon” so who knows?). 

Dylan decides he can’t prove Margot is the killer, so he decides to kill her himself by pushing her out the window. He thinks she is dead, so he then goes to turn himself in. 

We, the audience, think there’s no way Margot could be the killer since she was attacked, but if Dylan’s not the killer that leaves her free to be the killer. 

They also made a point of showing Margot repeatedly touching cuts on Allison’s thigh as if she was counting them. So I’m pretty sure she knows that Allison is not Lennon. Though she only figured that out now so honestly I don’t know what her motivation for being the killer would be.