Jane and Lisbon end up in a Wild West town when the own turns up dead on The Mentalist. "Red Letter Day" is the 19th episode of the show's fifth season.
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The Mentalist Season 5 Episode 19 Quotes

Jane: Don't you think it's odd, Homeland Security's fascination with a California serial killer?
Lisbon: Everything about Bob Kirkland is odd. You can add that to the list.

Jane: They argued.
Deb: How do you know they argued?
Jane: He is dead.