S3, E13: In this special Halloween episode, Aria, Emily, Hanna and Spencer are looking forward to some good Halloween fun now that the traumatic events with Nate are behind them. But once aboard the Rosewood Ghost Train, the girls are in for much more than just some childish tricks or treats. With "A" running a muck and unexpected party-goers popping up at every turn, this Halloween event becomes one killer party. Plus, musical guest star Adam Lambert (American Idol) performs his songs "Trespassing" and "Cuckoo" during the Halloween festivities.