Things are getting spooky on Pretty Little Liars.

In a special Halloween-themed episode of the ABC Family hit (airing Tuesday, Oct. 23), a somber Aria Montgomery (Lucy Hale) chats up special guest star Adam Lambert, who appears as himself.

"I can't tell if you're having fun or not," Lambert tells Aria while aboard a speeding train.

"No!" Aria says, smiling. "This is incredible. Is this fun for you?"

Lambert responds, "This is absolutely fun. Did you come alone?"

"Yeah, my boyfriend couldn't make it tonight," Aria explains.

After some idle banter, Lambert says goodbye to prep for his next set, and Aria vows to be in the front row. When she's not looking, a masked stranger discreetly pours a white powder into Aria's drink -- presumably to make her lose consciousness.

Pretty Little Liars airs Tuesday, Oct. 23, at 8 p.m. EST on ABC Family. The series returns full-time in January.