Chelsea O'Toole

Hank treats a chatty socialite who disappears before he can diagnose her. Meanwhile, Divya is called to Adam's estate and finds herself surprised at how scared she becomes when his health begins to fail.

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.

Spencer and Emily make plans to visit a nearby college, but they have very different agendas for their time spent on campus. Spencer's singular focus to figure out Ali's apparent connection to the school contradicts Emily's real fears about her plans for after graduation. And, after a stinging attack by "A," Aria and her brother, Mike (recurring guest star Cody Allen Christian), don't see eye to eye regarding what's best for their parents. Meanwhile, Hanna becomes increasingly frantic when she makes another horrifying discovery among her mom's things, leading her to make a desperate move - with disastrous results.