4-D (The X-Files)
"4-D" is the fourth episode of the ninth season and the 186th episode overall of the American science fiction television series The X-Files. The episode first aired in the United States on December 9, 2001 on the Fox network. It was written by Steven Maeda and directed by Tony Wharmby. 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. The episode earned a Nielsen rating of 5.1 and was viewed by 5.38 million households. It received mixed to positive reviews from television critics.
The show centers on FBI special agents who work on cases linked to the paranormal, called X-Files; this season focuses on the investigations of John Doggett (Robert Patrick), Monica Reyes (Annabeth Gish), and Dana Scully (Gillian Anderson). In this episode, a vicious murderer named Erwin Lukesh, capable of jumping between parallel universes, shoots Doggett using Reyes' gun. Brad Follmer opens an investigation to figure out the truth. Reyes eventually deduces that Lukesh is the real murderer.
Maeda wrote the episode after being inspired by the situation of a real-life French journalist, Jean-Dominique Bauby, who had been paralyzed and could only communicate by blinking his left eyelid. The character of Lukesh was in part inspired by Alfred Hitchcock's Psycho and was created by Maeda in the hopes that he would go on to be a memorable villain. Effects expert Mat Beck created the unique visual sequence that showed Doggett and Lukesh traveling between the different universes. To create the effect of a parallel universe, every scene in the episode's teaser was flipped so that the mirror image was shown.