Now that the characters of Pretty Little Liars have fully mastered the art of the hyperrealistic rubber mask, it has become harder than ever to determine who can be trusted. As Aria and Hanna sat on the steps of the police station discussing men they've murdered and men they're not engaged to, the camera panned slowly to a cop in a car watching them. Though he appeared to be a normal bald police officer, he was actually someone else wearing a mask. So who is wearing the cop mask on Pretty Little Liars?
The cop continued to be a majorly ominous threat throughout the episode and he was next spotted watching Emily exit Alison's house. At first it seemed like he could be A.D., or Elliot Rollins returned from the dead (he did love using those masks, after all.) The cop could even be both, since the identity of A.D. remains a mystery. However, his motives were definitely nefarious, so when Alison invited the cop into her home it became clear something bad was about to go down. He tackled Ali and she grabbed for his face, ripping off the mask and appearing to recognize Elliot — or think that she did. In the moment, it wasn't entirely clear who he was, but Alison was certain.
But this theory went out the window when Hanna and Spencer went to go dig up Elliot's grave and found him just where they left him. Although that makes some things more confusing, it does actually clear up others. Elliot is definitely dead and A.D. was definitely the cop in the mask, as evidenced by the final shot of a mysterious hooded figure putting the mask on their desk. This also means Elliot isn't A.D., which cuts another suspect from that list.
Alison is the only one to catch a glimpse of the face behind the mask and it could be telling that she thought it was Elliot (or, rather, Archer). Perhaps it was only the ramping tension over Elliot's potential disappearance that was making her see things, but it's also possible that A.D. resembles Elliot. That would mean A.D. was a man and there is one suspicious man walking around Rosewood who shares at least a passing resemblance to Archiott: Noel Kahn.
It may be a long shot, but the two are not physically dissimilar and they could be mistaken for one another in the heat of a fight. Noel did just return in the last episode, "Along Comes Mary," and he's definitely up to something. Even if he's not A.D., Noel could be working for them.
But with nothing confirmed yet, fans can only speculate.