In the opening episode of Heroes' fourth volume, Claire delivers a warning to Parkman: beware of Nathan. Dude is up to no good.
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Check out this clip from the volume four premiere. In this scene from "A Clear and Present Danger," Peter speak to Suresh in the latter's taxi.
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Heroes Season 3 Episode 14 Quotes

I'm a God-fearing man. I just want what's best for our country.

Nathan

The threat is real.

Nathan