VIDEO: Adam Lambert Guest Stars On 'Pretty Little Liars' Halloween Special

The Rosewood regulars found themselves on a Halloween party train that, aside from a brief musical guest appearance by past American Idol winner Adam Lambert, was mostly horrifying. This episode was again haunted by the usual deceit, deception and destruction that the Pretty Little Liars — Aria (Lucy Hale), Spencer (Troian Bellisario), Hannah (Ashley Benson) and Emily (Shay Mitchell) — face on a regular basis in trying to escape the mystery “A” who wreaks havoc on their lives.

Shortly after Garrett (Yani Gellman) revealed to Spencer that he actually didn’t kill Alison (Sasha Pieterse), and that Aria’s dad may have something to do with her going missing, Garrett himself wound up dead and shoved into a crate. Aria, meanwhile, got drugged at the party and wound up locked in the same crate, only to be set free at the very end of the episode. After the girls rescued Aria, another body was discovered stowed away in a beverage cart.

With regard to the loss of Garrett, Pretty Little Liars executive producer Marlene King had given clues as to who would face the end of the line in this episode. “It really goes back to our theme song, 'Two can keep a secret if one of them is dead,'" King told THR. "This person is about to reveal a huge secret to the Pretty Little Liars, which they will eventually find out in season 3B, but this person is killed because he's about to reveal a big secret. And that secret involves the night Alison went missing."

All of these loose ends, particularly — "Is it Alison's body in the body bag?" and "Who the hell is 'A'?" — will have to wait until Pretty Little Liars returns to the air on ABC Family after a mid-season break on January 8, 2013, at 9 p.m. EST. —Hal Sundt

Check out a clip here: