"Memento Mori" is the fourteenth episode of the fourth season of the American science fiction television series The X-Files. It premiered on the Fox network on . It was directed by Rob Bowman, and written by series creator Chris Carter, Vince Gilligan, John Shiban and Frank Spotnitz. "Memento Mori" featured guest appearances by Sheila Larken, David Lovgren and Morris Panych. The episode helped to explore the overarching mythology, or fictional history of The X-Files. "Memento Mori" earned a Nielsen household rating of 15.5, being watched by 19.1 million people in its initial broadcast. The title translates from Latin as "remember that you will die."