what does episode 2 (twin peaks) refer to?
It is the third episode of the first season of the American mystery television series "Twin Peaks".
Episode 2 (Twin Peaks)
"Episode 2", also known as "Zen, or the Skill to Catch a Killer", is the third episode of the first season of the American mystery television series "Twin Peaks". 
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Episode 2 (Twin Peaks) [SEP] Introduction
It has since influenced, and been parodied by, several subsequent television series. Academic readings of the episode have highlighted its depiction of heuristic, "a priori" knowledge, and the sexual undertones of several characters' actions.