Surf the Halls by Sarah Stegall Copyright © 1994 by Sarah Stegall Written by Paul Brown Directed by Stephen Surjik Like many viewers, I have been waiting for an episode that lets Dana Scully take a case, and allows her own investigative powers to shine. So when Mulder walks in at the beginning of “Excelsis Dei” and finds her in the middle of a case, I was thrilled. Agent Scully goes to bat for a nurse (Teryl Rothery) who claims to have been raped by an invisible entity. Mulder is immediately skeptical–there’s a rare turn- -pointing out that while they…