The title of the 3/8/10 episode of Castle is "The Mistress Always Spanks Twice." It deals with the underground world of sex clubs.
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Castle Season 2 Episode 15 Quotes

Castle: Did you just use the word "veritable" in a sentence?
Beckett: Yes, I did.
Castle: Sexy!
Beckett: You should hear me say "fallacious."

Castle:Alright, what aren't you telling me!?
Beckett:Oh so much Castle, so very very much.

Castle Season 2 Episode 15 Music

  Song Artist
Song Patterns Band of Skulls
Song SuperConductor Beautiful Small Machines
Ghost in the machine standalone Standalone Ghost In The Machine iTunes