A murder by the Red John copycat killer is at the center of this discussion. It takes place on The Mentalist season finale, "Red Sky in the Morning."
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A-ha! Jane appears to come to a realization in the season finale of The Mentalist. It's titled "Red Sky in the Morning."
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Jane has a lot to think about on the second season finale of The Mentalist. Specifically, of course: Red John.
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The Mentalist Season 2 Episode 23 Quotes

Tiger tiger burning bright in the forest of the night.

Red John

I hate the internet.

Van Pelt