The Pretty Little Liars Halloween episode Season 3, Episode 13: “This Is a Dark Ride”) brought up a slew of new mysteries, including why Byron Montgomery (Chad Lowe) was with Alison (Sasha Pieterse) the night she died, and who tried to murder Aria (Lucy Hale). But one of the most puzzling new questions hasn’t been discussed as much: How did Alison’s dead body wind up in the ice box on the Halloween party train?

Before this episode, we had a few sketchy clues as to who had originally stolen Ali’s body from the graveyard. Did the same person (or group of people) bring it on the train?

Here are three possibilities.

The “A” team. On Season 3, Episode 12: “The Lady Killer”, Mona (Janel Parrish) and Toby (Keegan Allen) had a plan to meet the Liars at Alison’s grave. That plan changed, of course, once Emily (Shay Mitchell) decided to get away from everyone and stay at a lake hotel, but their original plan could be a sign that the “A” team knows all about Alison’s grave robbery. Plus, “A” sent the Liars a photo of a large box that same night, that looked like it was just the right size for a body. Days after the grave robbery, the Liars found dozens of photos taken of them standing over Ali’s grave, clearly a threat from “A.”

Since we know that the “A” team was on the train on Halloween, any one of the masked monsters could have snuck Ali’s body on board. The only snag here, we think, is that Toby looked genuinely shocked when Alison’s body bag came tumbling out of the ice.

Jenna and Noel (and Lucas). Once Emily’s memory started to come back from the night she was drugged and abandoned at Ali’s empty grave, she remembered seeing Jenna (Tammin Sursok) in the driver’s seat of the car used to take her there. Jenna later admitted that she was driving Emily around that night, but claimed she didn’t drop her off at the graveyard. But Lucas (Brendan Robinson) was also spotted that night, and drugs were later found in his camera bag. Could they have been working together?

It’s possible that this is why Lucas and Jason (Drew Van Acker) were having a private conversation. Maybe Lucas was telling Jason that he knew where Ali’s body was, and who had stolen it. 

An unknown third party. We still don’t know who that mysterious blonde is who showed up at the masquerade ball in the Season 2 finale (Season 2, Episode 25: “UnmAsked”). And we still don’t know who visited Mona in the hospital after she was sent to Radley, someone who Mona considered the authority. Whether or not that person is one and the same, they could be responsible for dumping Ali’s body. 

What do you think? Share your thoughts in the comments!

Catch the return of PLL Season 3 on Tuesday, January 8, 2013 at 8 p.m. ET/PT on ABC Family.

Molly Friedman is an editor at Wetpaint Entertainment. Follow her on Twitter @MollyFriedman.

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