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Adam Lambert cakes on makeup, puts in fangs, and wraps himself in a cape as a musical guest on the Halloween episode of Pretty Little Liars.

VIDEO: Watch Adam Lambert Make 'PLL' Crazy!

The self-professed "glampire" will share a scene with Lucy Hale's character Aria. He tells ET, "I don't suck blood her or anything. I'm friendly. I'm Adam Lambert dressed as a vampire. I'm not an actual vampire."

RELATED: 'PLL' Halloween Costumes, Revealed!

Without letting the tightly-kept secret plotline slip, Lucy, dressed as Daisy Buchanan from The Great Gatsby, reveals the episode "reminds [her] of the game Clue." She says, "Last Halloween episode, it was a pretty big deal, but they are pulling out all the stops for this one. They're building things and we took over a whole new stage because usually we have two stages, but this is a new stage and they're building a train because the party takes place on a train and things start to happen on this train."

VIDEO: 'PLL' Stars Preview Halloween Horrors

Havoc will break loose on the rails when Pretty Little Liars airs Tuesday, October 23 on ABC Family. For one key character, this is a one-way trip. Someone won't make it out alive.

PHOTOS: Celebrity Halloween Costumes