Sparia is deciphering the log book and find out that Ali (under the pseudonym Vivian Darkbloom) had stayed there before. The sketchy innkeeper returns and the girls scatter back to Rosewood.
Spencer finds Toby outside Jason’s house cleaning up the mess from the fire, and he tells her that the authorities said it wasn’t an accident. She tries to make amends, but he doesn’t really want anything to do with her so she gets upset and leaves.
The girls go to the ball, all in masks making it really difficult to see who is who. Caleb surprises Hanna after saying he wasn’t going to be there, and Aria runs off into the obscene amount of decorations. She’s being watched by someone in a black mask. But don’t fear, Ezra is here! He came back for her, saying that he couldn’t stay away and that he loves her. They go back to the dance with their masks on, and he decides to take them off and go public! It was beautiful.
Meanwhile, Mona and Spencer have a chat. Mona recalls a story where she found Ali (aka Vivian) in Brookhaven at the same store where she bought the costumes for the masquerade ball. She said that Ali was spying on someone and offered to keep her secret if she made Mona popular. Then Ali was never seen again. So Spencer and Mona take off back to the Lost Woods Resort after Spencer concludes that Ali was in fact spying on A, and that Room 2 was never booked or available.
Spencer charms the sketchy innkeeper while Mona obtains a key to Room 2. They go to Room 2 and discover A’s lair filled with creepy photos of Ali and all the girls and lots of awkward paraphanelia. Mona finds sketches of A’s costume for the ball, which looks like the Black Swan (no A is not Natalie Portman). Mona offers Spencer a piece of gum to which she declines because she picks up Ali’s diary to find the same kind of gum wrapper as the bookmark in the diary. Mona goes outside to “call Hanna” to warn them about the Black Swan, who we see at the ball talking with Jenna and Lucas!
Mona comes back dressed in a black hoodie and black pants and black gloves. OMGJKF:HDSJHG:jk Mona is A!