"Underneath" is the twelfth episode of the ninth season of the American science fiction television series The X-Files. The episode first aired in the United States on March 31, 2002 on the Fox network. The episode was written and directed by executive producer John Shiban. The episode is a "monster-of-the-week" episode, a stand-alone plot which is unconnected to the mythology, or overarching fictional history, of The X-Files.