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.

Eighteen hours later, they are spotted by a Canadian fishing vessel; however, in that short span of time, the young crew members have undergone rapid aging.

Dana Scully (Gillian Anderson) is asked by Fox Mulder (David Duchovny) to visit the ship's sole surviving crew member, Lt. Harper, who has been quarantined at the Bethesda Naval Hospital because of her being a doctor.

Mulder believes that a "wrinkle in time" exists there, and that Ardent was the subject of government experimentation related to the Philadelphia Experiment from World War II.

They also find the wizened commanding officer of Ardent, Captain Barclay, who claims that "time got lost" after his ship encountered a "glowing light" in the ocean.

Scully develops a theory that Ardent is sailing near a metallic object beneath the ocean, and that it has caused free radicals to rapidly oxidize their bodies and age them.

Scully learns from blood tests that the contaminated water causes rapid oxidative damage and dramatically increases sodium chloride in the body.

Scully comes to at the hospital, where she is told that her written observations on the case helped naval doctors reverse their aging and save Mulder from near-certain death.

[1] Prior to this episode being produced, the Canadian Forces had granted permission for the show to use HMCS Mackenzie (a decommissioned destroyer) for the production of "Colony" and "End Game".

[2][3] Series creator Chris Carter, wanting to take full advantage of this rare opportunity, asked Howard Gordon to write another episode that could also be filmed on the ship.

[2] To ease filming, the producers sought out a set that they could use as both a bar and a hospital—a task initially believed "impossible" by the show's location scouts.

There are so many nice little moments here [...] it's a script that pauses from the constant horror the show had been serving up for several episodes in a row to just tell an unsettling, ultimately moving tale of two friends who look into the abyss and somehow don't fall.

"[12] Robert Shearman, in his book Wanting to Believe: A Critical Guide to The X-Files, Millennium & The Lone Gunmen, rated the episode three-and-a-half stars out of five.