4x01 Herrenvolk (pt. 2)

As Mulder's mother lies dying, he and Scully are given tantalizing glimpses of a plan to secretly catalog – and clone –  human beings.  Only by putting the pieces together can they hope to save Mrs. Mulder's life.

4x02 Unruhe

Someone is abducting, mutilating, and murdering the inhabitants of a small town.  The primary evidence is a series of photographs depicting the killer's psychotic fantasies.

4x03 Home

While investigating the death of an infant in a close-knit rural community, Mulder and Scully uncover an ever darker family secret.

4x04 Teliko

African American men are disappearing.  Their bodies, when found, are dead white – drained of pigment.  Were they killed by a virulent new disease?  Were they murdered?  Or does the answer lie elsewhere.

4x05 The Field Where I Died

In an effort to prevent a mass suicide at a fanatical religious cult, Mulder and Scully interrogate one of the wives of the polygamous cult leader.  Under hypnosis, her accounts of her past lives –  and deaths –  are inexplicably tied to the agents' own.

4x06 Sanguinarium

At a busy – and lucrative – cosmetic surgery clinic, doctors are murdering patients with the tools of their trade.  Several clues point toward demonic possession.

4x07 Musings of a Cigarette Smoking Man

The secret biography of a sinister, all-powerful conspirator is discovered by Frohike, who's life may be in mortal danger by its author.  Some old mysteries are cleared up – and some new ones created.

4x08 Paper Hearts

Prompted by a series of prophetic dreams, Mulder re-opens the case of a convicted child killer.  The murderer claims to know the circumstances of Samantha Mulder's abduction.

4x09 Tunguska (pt. 1)

Diplomatic couriers are bringing a lethal alien life-form into the United States.  Mulder and Scully's investigation points to a high-level international conspiracy beyond even their comprehension.

4x10 Terma (pt. 2)

Stranded in the gulag, Mulder discovers the effects of the alien toxin – firsthand.  In Washington, Scully battles a corrupt U.S. senator to keep their investigation alive.

4x11 El Mundo Gira

Fear, jealousy, superstition, and prejudice converge when a young female migrant worker is killed by a mysterious yellow rain, and the blame falls on her paramour who they claim is El Chupacabra.

4x12 Kaddish

Someone – or something – is killing the members of an anti-Semitic gang.  To find the truth, Mulder and Scully delve into the ancient texts of Jewish mysticism.

4x13 Never Again

On a solo assignment out of town, a lonely Scully meets Mr. Wrong – a single guy who thinks his new tattoo is talking to him.

4x14 Leonard Betts

A headless corpse escapes from a hospital morgue.  Mulder and Scully investigate; what they find leads them to the jagged dividing line between life and death.

4x15 Memento Mori

Scully learns she has inoperable cancer – of the same type that killed nearly a dozen female UFO abductees.  While she undergoes radical treatment, Mulder works desperately to unravel the conspiracy behind her disease.

4x16 Unrequited

A marine Corps prisoner of war, abandoned in Vietnam by his superiors, returns to the United States with a vengeance –  and a special talent for hiding in plain sight.

4x17 Tempus Fugit (pt. 1)

A former UFO abductee is killed in a catastrophic plane crash.  Mulder suspects a conspiracy – and a cover-up.

4x18 Max (pt. 2)

Mulder and Scully gets clones to proving alien involvement in the crash of Flight 549.  As they do so, they trigger a massive military disinformation campaign – and the deaths of several friends and colleagues.

4x19 Synchrony

For centuries, scientists have debated whether time travel is possible – and if it ever will be.  For Mulder and Scully, this age-old conundrum is the key to solving several baffling murders.

4x20 Small Potatoes

Mulder and Scully investigate several not-so-blessed events in a small southern town.

4x21 Zero Sum

Walter Skinner makes a deal with the devil – a.k.a. the Cigarette Smoking Man – in an effort to prevent Scully from dying of cancer.

4x22 Elegy

Several young women have been murdered on Mulder and Scully's home turf.  Their prime suspect is a mentally disabled man, Harold Spuller, who has been beset by a series of frightening apparitions.

4x23 Demons

After experiencing a series of blackouts and seizures – and what might be the recovery of repressed memories – Mulder gains new insights into his younger sister's abduction.  However, while taking his inner journey, he may also have murdered two people.

4x24 Gethsemane

When a controversial scientist claims to have discovered evidence of extraterrestrial life, Mulder and Scully find their lives – and belief systems in grave peril.