"Episode 4", also known as "The One-Armed Man",^{[nb 1]} is the fifth episode of the first season of the American mystery television series Twin Peaks. The episode was written by Robert Engels, and directed by Tim Hunter. "Episode 4" features series regulars Kyle MacLachlan, Piper Laurie and Richard Beymer, and introduces series co-creator David Lynch in the role of Gordon Cole.

Hunter's directing of the episode was inspired by Otto Preminger's 1945 film Fallen Angel, making use of small sets and long depth of field shots. Engels has identified several 1960s television series—The Wild Wild West, Mayberry R.F.D. and The Fugitive—as being influential to the series as a whole.

First airing on May 3, 1990, "Episode 4" was viewed by approximately 19 percent of the available audience during its broadcast, marking an increase in viewers from the previous week. "Episode 4" has received positive reviews from critics.

"Episode 4" was the first of the series to be written by Robert Engels; Engels returned to pen a number of other episodes across both seasons.^[7] The episode was directed by Tim Hunter, who would also go on to helm "Episode 16" and "Episode 28" in the second season.^[8] Hunter had known series co-creator David Lynch from their time studying together at the American Film Institute.^[9] Engels had been brought on board by the other creative force in the series, Mark Frost, who felt that Engels' sense of humor would be well-suited to the series' style.^[10] Engels found the pace of the series' writing to be quite fast, noting that Frost and Lynch would outline the plot of an episode in a matter of hours—Engels had previously been used to spending days at a time working on similar amounts of material with writing crews on other programs.^[11]

Hunter recalls being pleasantly surprised to learn that Russ Tamblyn and Richard Beymer had been cast as regular characters in the series, having enjoyed the early work of both actors during the 1950s and 1960s.^[12] Tamblyn improvised elements of his performance, including a magic trick involving two golf balls, which was something he had learned and wished to include during his role in the episode.^[13] The character of Gordon Cole, first played by Lynch in this episode as a voice in a telephone call, was conceived as being hard of hearing; this was because Lynch liked the idea of delivering his lines in a loud voice, and worked backwards to establish a reason for this. Engels wrote most of Cole's dialogue over the series, having had experience with his own mother being similarly hard of hearing.^[14]

Engels felt that the three largest influences on the series as a whole were the 1960s television series The Wild Wild West, Mayberry R.F.D. and The Fugitive—the inclusion of a one-armed character in Twin Peaks was a direct homage to the latter of these.^[15] Engels has also noted that the series would make use of normal, conventional storylines and everyday occurrences as a "familiar" framework, allowing subtle details to seem slightly more unusual against this backdrop—he particularly cites this episode's parole hearing for Hank Jennings as an example, as it offers nothing out of the ordinary other than the single domino which Jennings is playing with at all times, drawing attention to the item as it is the only thing which seems out of place.^[16]

Hunter's direction in some scenes was inspired by Otto Preminger's work on the 1945 film noir Fallen Angel. That film featured several scenes shot in tight spaces with a very small mise en scène; Hunter found himself using several of Preminger's techniques to make the most out of several of the episode's smaller sets such as the RR Diner.^[17] Several scenes in the episode were also shot using a split diopter lens, allowing for a greater depth of field. For example, a scene featuring Sherilyn Fenn and Richard Beymer talking had the actors at either side of a room; the split diopter lens allowed for both of them to still be in sharp focus.^[18] The episode ends with a shot featuring a Dutch angle; Hunter was the only director on the series who Frost and Lynch allowed to use this shot, which was otherwise forbidden.^[19]

"Episode 4" was first broadcast on the ABC Network on May 3, 1990. In its initial airing, it was viewed by 11.9 percent of US households, representing 19 percent of the available audience. This marked a slight increase from the previous episode, which had attracted 11.3 percent of the population and 18 percent of the available audience.^[21] "Episode 4" was the forty-fourth most watched broadcast on American television that week.^[22]

The A.V. Club's Keith Phipps rated the episode a B, deeming it "a 'normal' episode for the series".^[20] Phipps praised Al Strobel's performance, and felt that the episode served to highlight "Cooper's investigation-by-coincidence technique", while describing the character of Madeline Ferguson as "an embodiment of this series' obsession with duality".^[20] Writing for Allrovi, Andrea LeVasseur rated the episode four stars out of five.^[23] Television Without Pity's Daniel J. Blau offered mixed reactions to the episode's acting; he found Sheryl Lee, James Marshall and Grace Zabriskie to have been poor, but praised Kyle MacLachlan, Ray Wise and Dana Ashbrook for their performances.^[24]