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Trust no one
Deep Throat

"The Erlenmeyer Flask" is the twenty-fourth episode and first season finale of the The X-Files. Written by series creator Chris Carter and directed by R. W. Goodwin, the episode helped explore the series' Mythology arc.

It first aired in the United States on May 13, 1994 on the Fox network.


Stakes are high during this thrilling conclusion as the agents get closer to the conspiracy and learn their dark secret.


In Ardis, Maryland, a high-speed police chase unfolds at a waterfront. The driver of the car is Dr. William Secare. Although he is shot, Secare escapes into the water, and the police find green blood on the spot where he was shot.

Soon afterwards, "Deep Throat" (Jerry Hardin) approaches Fox Mulder with Secare's case, saying he is of major importance to reveal the truth. When investigating the case, Mulder and Agent Scully visit Dr. Terrance Berube (Ken Kramer), a scientist working in Gaithersburg, Maryland whose car was involved in the Secare incident. That night, Deep Throat meets a second time with Mulder, and insists he continue on the case, despite Mulder's uncertainty on what he's supposed to be looking for.

That night, Dr. Berube is met by the "Crew Cut Man", who kills him and makes the death look like a suicide. While investigating the crime scene, Mulder finds a liquid-filled erlenmeyer flask with a typed label "Purity Control" on the underside, which he gives to Scully. Scully takes the flask to Georgetown University, where she meets Dr. Anne Carpenter (Anne De Salvo), who examines the contents.

Meanwhile, Mulder heads to Berube's house and finds keys for a storage facility. Dr. Secare calls Dr. Berube's office, but Mulder answers the phone feigning to be Berube. Secare tells him about the secret government project which Mulder wants to reveal to the public.

In the meantime, the Crew Cut Man eavesdrops on the conversation from a van in the street. Secare collapses during the phone call. A bystander calls an ambulance. A poisonous gas emits from Secare's body when the paramedics perform a needle decompression. Secare gets up and flees from the ambulance.

Tanks Hybrids Zeus Storage Erlenmeyer Flask

Tanks found by Mulder.

Mulder arrives at Zeus Storage and finds five men suspended in horizontal, rectangular liquid-filled tanks, as well as a sixth empty tank. Dr. Carpenter reveals that the "Purity Control" flask contains a sample of bacteria that doesn't exist anywhere in nature and can only be described as extraterrestrial. Meanwhile, Mulder is pursued when he leaves the storage facility but escapes. He returns the next day with Scully. By then, however, the room is completely empty. Deep Throat arrives, revealing that Berube was experimenting on humans with extraterrestrial viruses. Six terminally ill volunteers were experimented on, and all had begun recovering. When it was ordered that they be destroyed, Berube helped Secare escape.

Scully returns to Georgetown University, only to find out that Dr. Carpenter and her entire family have been killed in an automobile accident. Mulder returns to Berube's house and finds Secare in the attic, and tries to convince him not to leave, but Secare is then shot to death by the Crew Cut Man.
Dana Scully Erlenmeyer Flask Alien Fetus
Mulder passes out from exposure to the gas escaping from Secare's wound, and is captured. Deep Throat meets Scully outside of Mulder's apartment and says that he may be able to make a deal with the people who captured Mulder. He gives Scully the credentials necessary to enter the High Containment Facility at Fort Marlene. When prompted by a security guard for a project password, "Purity Control" allows her to pass. There, Scully finds an alien fetus contained within liquid nitrogen.

Scully meets Deep Throat on a bridge. He refuses to let her be the one to make the deal, so he presents the fetus to the Crew Cut Man, who shoots him seconds later. Mulder is released from the Crew Cut Man's van as he drives off. Scully tends to Deep Throat, who utters his last words before dying: "Trust no one."

Several weeks later, a despondent Mulder calls Scully to inform her that the X-Files have been shut down. Meanwhile, in a scene mirroring the conclusion to the pilot, the Smoking Man stores the alien fetus in the massive evidence room within the Pentagon.


Syndicate; Purity Control;


"Trust... no... one...."

- Deep Throat to Agent Scully


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