When Deep Throat points out a news story about a fugitive who apparently drowned, Mulder and Scully cannot see what makes the case special but follow it up anyway. With Deep Throat's insistence, they discover evidence of a secret government project code-named Purity Control, which uses human test subjects and infects them with extraterrestrial DNA. However, the evidence and everyone who has seen it is quickly being eliminated.

In the claustrophobic isolation of a remote outpost in Alaska, Mulder and Scully investigate the horrifying deaths of scientists.

Mulder and Scully search for a humanoid killer whose savage murder spree reoccurs every thirty years.

Mulder and Scully receive information from Deep Throat about a UFO that was shot down over Iraq and has been secretly transported to the US. However, Deep Throat then intentionally misleads the agents to prevent them from discovering the truth.

Eugene Tooms is released from the sanitarium, and Mulder becomes personally involved to ensure that he is caught in the act of getting the last human liver he needs to go into hibernation for another 30 years.

The agents' first case takes them to Oregon to investigate the unsolved murders of several high-school classmates.

When two fathers on opposite sides of the country are inexplicably murdered at the exact same time in the exact same way, Mulder and Scully are called in to investigate. When they discover that the two fathers' eight-year-old daughters are identical twins, they realize that something even stranger is going on.

When a group of loggers in the Washington State National Forest disappear in the same way that another group disappeared 50 years ago, Mulder and Scully go along to investigate and find themselves trapped in a cabin surrounded by flesh eating insects that only attack at night.

When death row inmate Luther Lee Boggs claims to be psychic and can lead Mulder to a serial killer in return for a lesser sentence of life in prison, Scully becomes an unwilling believer when Boggs tells her that she can communicate through him with her recently deceased father.

Mulder and Scully head to Ellens Air Force Base to investigate the mysterious case of a military test pilot who disappeared after experiencing strange psychotic behavior. While on the case, Mulder meets a mysterious man dubbed 'Deep Throat' who claims to have classified information about his investigations into the paranormal.

Mulder puts the future of the X-Files in jeopardy when he heads to a UFO crash site being rapidly covered up by the military. He is arrested, and while in jail he meets Max Fenig, a UFO nut whose NICAP group has followed Mulder's work on the X-Files. When Mulder is released, Scully urges him to return to Washington to face his superiors and try to save his job, but Mulder finds out that Max is more than meets the eye and ignores Scully to try and save him instead.

As Section Chief Blevins expresses his concern with the direction of the X-Files, Mulder becomes obsessed with solving a case that closely parallels an encounter he experienced as a child: the abduction of his kid sister, Samantha.

Mulder and Scully investigate the death of a scientist working on advanced propulsion technology. The mentally challenged janitor Roland, who has secretly been completing the scientist's work, is the prime suspect.

Mulder and Scully investigate the deaths of two men believed to have been killed by a powerful psychokinetic force.

An old Oxford girlfriend of Mulder's asks for his help on an international case concerning the unexplainable execution of several British dignitaries, and they encounter an assassin who can produce fire from his bare hands.

Mulder becomes the target of someone from his past named John Barnett. He was a jewelry store robber with an itchy trigger finger that Mulder sent to prison when he first joined the Bureau. The only problem is that Barnett died four years ago.

A young man who has the power to heal people with his touch begins to question his gift when people start dying after he has supposedly healed them.

A series of sexually-oriented murders, which are identical except that the killer appears to be both male and female, draws Scully and Mulder to an Amish-type community of people called the Kindred.

After a detective and his former partner die in unexplained circumstances, the accidents are linked to a little girl who witnessed both deaths. Mulder believes that she may be the reincarnation of a policeman murdered by his colleagues.

Mulder and Scully track a legendary creature that has roamed the New Jersey countryside for over forty years.

When FBI Agent Jack Willis and bank robber Warren Dupre are both shot at the same time during a robbery attempt, Dupre dies when Willis is brought back to life. When Willis rushes out of the hospital and begins acting strangely, Mulder concludes that Dupre has come back to life in Willis' body.

Mulder and Scully travel to a Native American reservation to investigate the death of a man who was mistaken for a wild animal and may have been the legendary Manitou, a man who can shape-shift into a beast.

It's Halloween, and Mulder and Scully are investigating the strange death of a corporate executive in a sophisticated high-tech building.

Mulder and Scully are contacted by a communications specialist from NASA who shows them evidence of sabotage in the space programme.