Pretty Little Liars Season 4B began with the question: Who’s in the box? Not only are the Liars not much closer to discovering who’s in Ali’s grave, but perhaps more importantly, they have no idea who did it. Fortunately, we’ve garnered some new clues from the Season 4 finale. Here are our best guesses at who killed the girl in Ali’s grave.

Melissa

After last night’s Season 4 finale, Melissa is at the top of our list of possible suspects. Not only did she have her mother get a defense attorney, but she whispered a secret involving the murder in her father’s ear. And it certainly shocked him. We think Melissa may have been the one who killed the girl in Ali’s grave — perhaps because she thought it was Ali herself. She was beyond enraged with Ali for both spending the weekend with Ian at the Hilton Head Resort and for stealing the N.A.T. Club videos from Ian’s computer. Did she kill the wrong girl, thinking it was Ali?

Ali’s Twin

We think there was another DiLaurentis girl out the night of Ali’s disappearance: Ali’s twin. In the book series the TV show was adapted from, Ali’s twin Courtney was “A.” Though the show hasn’t followed the exact plot of the books, we wonder if they will be able to pass over such a juicy plot twist – even if it is known by readers of the book series. If Ali does have a twin, we think she might have been the one sending her threatening messages. We also think she escaped from Radley, which is why Mrs. D. was so anxious on the phone that night. Did she also mistake this girl for Alison, going after her before she went after Alison? Alternately, did she see Mrs. Grunwald pull Ali from that grave, and decide to replace her body with someone else’s in a weird attempt to make amends with her sister?

Mona

There are knew at the time that Alison didn’t die that night. Top of the list: Mona. We know that she helped Alison escape from Rosewood, even if she did have ulterior motive. She gave Alison clothes, her car, and a somewhat peaceful night’s rest at the Lost Woods Resort. Did she go even further than that, killing another girl so that Alison would stay safely on the run? We’re still not sure what Mona’s motives are or were, but she seemed pretty dedicated to keeping Alison gone and/or safe.

Mrs. Grunwald

Credit: ABC Family

Another person who knew of Alison’s survival was Mrs. Grunwald. We don’t know much about this mysterious former house mother, even after her stint with the spirits in Ravenswood. How far would she go to protect Ali’s secret? We can’t imagine her going back to Rosewood to kill someone to keep Ali’s secret safe, but she did drive all the way from Ravenswood on a bad feeling. Maybe she had a bad feeling about the girl in Ali’s grave, too.

Who do you think killed the girl in Ali’s grave? Share your theories in the comments below!

Catch the next episode of Pretty Little Liars on June 10, 2014 at 8 p.m. ET on ABC.

Kayti Burt is a contributing writer for Wetpaint Entertainment with a penchant for all things pop culture. Follow her on Twitter and Google+!