The show centers on FBI special agents Fox Mulder (David Duchovny) and Dana Scully (Gillian Anderson) who work on cases linked to the paranormal, called X-Files.
"Three of a Kind" functions as a sequel of sorts to the fifth season episode "Unusual Suspects", concluding the story of The Lone Gunmen and Susanne Modeski, the woman who led to the creation of the trio.
While Mulder played a supporting role in "Unusual Suspects", the concept is reversed in "Three of a Kind", with Scully helping out The Lone Gunmen.
During a high-stakes poker game Lone Gunman John Fitzgerald Byers (Bruce Harwood) is thrown out after being exposed as a fraud at a government convention in Las Vegas.
Unbeknownst to Richard Langly (Dean Haglund) and Melvin Frohike (Tom Braidwood), Byers is still harboring an attraction to Susanne Modeski, a fellow conspirator who mysteriously disappeared almost ten years ago.
The Lone Gunmen cleverly trick Agent Dana Scully (Gillian Anderson) into coming to Las Vegas using a text to speech program.
After being confronted by Byers, Susanne reveals that she is pretending to have switched sides so she, along with her fiancee Grant Ellis, can slow progress on the government's harmful initiatives.
Langly reports to Timmy the next morning and is given his instructions: enter the meeting room using the provided pass and fire three rounds into Susanne Modeski.
[1] "Three of a Kind" functions as a sequel of sorts to the fifth season episode "Unusual Suspects", concluding a minor story-arc featuring The Lone Gunmen and Susanne Modeski, the woman who led to the creation of the trio.
[3] (Only David Duchovny's voice appears in the episode, during a scene in which The Lone Gunmen electronically synthesize it to convince Scully to travel to Las Vegas.
)[4] To compensate for this loss, co-executive producers Vince Gilligan and John Shiban decided to write an episode based around The Lone Gunmen.
The writers wanted to bring back several characters and unresolved plot lines, mostly notably the disappearance of Susanne Modeski, who had last appeared in season five's "The Unusual Suspects".
[2] Despite worries about going over budget, Fox allowed the production crew of The X-Files to film on location in Las Vegas, making the city one of the few to effectively "play itself" in the series.
However, only two days were allotted for Las Vegas, and the majority of the episode was filmed in California at the Century Plaza and Park Hyatt hotels.
[...] At first, the reaction was sort of lukewarm, then all of a sudden someone realized that this was The X-Files, for heavens sake, seen by I-can't-tell-you-how-many millions [...] then this huge bidding war broke out".
Robert Shearman and Lars Pearson, in their book Wanting to Believe: A Critical Guide to The X-Files, Millennium & The Lone Gunmen, rated "Three of a Kind" two-and-a-half stars out of five, calling the episode "likeable and good-natured, and utterly redundant, this passes forty-five minutes pleasantly enough, but you'll be hard pushed to remember them afterwards".