While Mulder served in the Violent Crimes Division of the Bureau, he assisted in the capture of the lethal murderer, John Barnett. During the criminal's trial, Barnett threatened to return and eliminate Mulder for his damaging testimony. In prison, Barnett was subjected to genetic manipulation, by Dr. Ridley, in order to reverse his aging process. Barnett escapes from prison in a younger form and stalks Agent Mulder. Mulder shoots Barnett after he attempts to execute Agent Scully. As military doctors feverishly work to save the dying Barnett, government officials, including CSM, hover in the background waiting for Barnett to reveal the location of Dr. Ridley's coveted Fountain of Youth research.
Eps: Young At Heart (1X15)

Originally Section Chief Blevins, under the direction of the Cigarette-Smoking Man, assigned Agent Dana Scully to work with Agent Mulder and report on the "scientific inaccuracies" of the X-Files. Recently however, S.C. Blevins was revealed to be the Syndicate's Mole in the F.B.I., working from the inside to thwart and reign-in the powers of Assistant Deputy Director Walter Skinner. Blevins was later "sanitized" by the Syndicate to prevent the exposure of his secret connections to their group.
Date of Death: Unknown
Episodes: Pilot (1X79); Gethesmane (4X24); Redux (5X02); Redux II (5X03)

While Agent Scully deals with the sudden death of her father, Agent Mulder investigates the abduction of a young couple. Luther Lee Boggs, a death row mass murderer, contacts Agent Scully and Mulder claiming to have the psychic ability to see into the mind of the kidnapper. Manipulating Scully by channeling her deceased father, Boggs attempts to make a deal to save his life in exchange for the location of the kidnap victims. Following a final confrontation with Dana, Boggs reveals the location of the victims and promises Scully the opportunity to speak with her father only at his execution. Scully declines to appear and Boggs is executed for his crimes.
Date of Death: December 1993
Eps: Beyond the Sea (1X12)

As an "inside" informer, Deep Throat has aided Agent Mulder in the investigation of many cases. Unfortunately, Mulder was unaware that this insider had connections to the Syndicate, and was using him as a pawn to reveal and hide the truth as he saw fit. Deep Throat was seemingly murdered by the Crew-Cut Man while helping Agent Scully to recover the kidnapped Mulder. His dying words, "Trust No One"
Date of Death: May 1994
Episodes: various

While investigating a series of religiously motivated murders, Agent Scully and Mulder encounter Kevin Kryder. Agent Scully comes to believe that Kevin is a stigmatic, an individual that spontaneously exhibits the wounds of Christ. Unknown to the agents, Simon Gates, also known as the Millennium Man, has been sent on a dark purpose to eliminate all stigmatics from the world and, "usher in the new age". With the hellish ability to burn his victims with a touch, the Millennium Man is able to eliminate Kryder's protector, Owen Jarvis, and kidnap the chosen child. During their final encounter, Dana is able to save Kevin before Gates succumbs to death by paper shredder.
Date of Death: Unknown
Eps: Revelations (3X11)

While investigating a strange series of murders in which the victims were supposedly killed by their children, Mulder and Scully soon discover a common connection between the troubled teens. All were patients of Karin Matthews, a therapist that encourages victims of abuse to empower themselves and confront their abusers. Unbeknownst to the teens, however, Matthews has a dark past of her own filled with rage and abuse. Sheltering a multiple personality and a dark power to control vegetation, Karin Matthews is able to eliminate the "abusers" from her patients' lives. While attempting to eliminate Agent Mulder with her evil powers, Matthews is dispatched, lumberjack style, by Groundskeeper Ramirez.
Date of Death: Unknown
Eps: Schizogeny (5X09)