The X-Files S06 E10 Tithonus

"The truth is out there."

Assistant Director Kersh tries to tear Scully and Mulder apart when he partners Scully with a New York agent investigating Alfred Fellig, a freelance police photographer who conveniently shows up to document the scene of a death as soon as it happens. While the young hotshot agent is convinced that Fellig is murdering the people, Scully has other (paranormal) theories.