In order to get to the bottom of his cases, Nate often goes undercover. His background as an insurance investigator provides him with the necessary skill set to do so.
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Leverage Season 1 Episode 1 Quotes

Alec: I'm just very good at what I do.
Parker: This is the score! The score!
Alec: Age of the geek, baby.
Eliot: Somebody kiss this man so I don't have to.

Eliot: He tried to kill us.
Parker: More importantly he didn't pay us.
Eliot: How is that more important?
Parker: I take that personally.
Eliot: There's somethin' wrong with you.