- “The truth is still out there, but it’s never been more dangerous”
- — X, Sleepless
Although his real name was never revealed, he became known as "X" or "Mr. X" as Mulder would seek his assistance by marking an "X" in masking tape on his apartment window.
Sanitizing a WarehouseEdit
In 1989, X led a group of men who, wearing masks, entered a warehouse at 204 Fells Point Road, in Baltimore, Maryland, as the warehouse had been exposed to a release of ergotamine-histomine gas, a drug that was being stored there by the government and had been developed by Susanne Modeski. After the men under his command checked that the environment was safe for them to take off their masks, X entered and walked in a straight line, past three men who had been helping Modeski. X stared at the men before stopping in his paces after coming to Agent Mulder, who lay, drugged and half-naked, on the ground. He then ordered one of his subordinates to sanitize the area, while glaring down at Mulder, and, after his subordinate walked back to the group, he again focused his hard stare on the three men who were standing nearby. The next day, as Modeski tells the three men to reveal the truth about the Government, she is stopped in her tracks and forced into a car which takes her away. As the car drives off, X is seen in the back seat staring at the three men. — Unusual Suspects
A Reluctant InformantEdit
After Deep Throat was murdered, X became Fox Mulder's new contact on the inside of the conspiracy. He first contacted Mulder by phone telling him he had "a friend at the FBI" — The Host. They did not actually meet in person until some time later, when X offered Mulder information on the case about soldiers who had been experimented on to eradicate their need for sleep. X was reluctant to be helping Mulder and told him he didn't want to be there at all. It was at this meeting that X told Mulder he was not willing to sacrifice his life for the X-Files as Deep Throat had, implying that he had known him too. — Sleepless
After Scully's disappearance, Mulder went to see Senator Richard Matheson but was met by X before reaching his office. X told him there was nothing the Senator could do for him, there's nothing anyone could do, that it was beyond all of them. He also told Mulder the men behind Scully's abduction had only one policy: to deny everything. — Ascension
While Scully was lying in hospital on life support, Mulder taped the X to the window looking for help. He became frustrated when none was forthcoming. When Mulder was visiting Scully he saw a man take some test tubes of Scully's blood and chased after him. While stalking the man, Mulder was grabbed and threatened by X. Mulder became angry because when he looked for help X wasn't there and now he expected Mulder to do what he says and stop searching for the men who put Scully in that state. With this encounter, it became apparent to Mulder that X was no Deep Throat, and that X believed that he controlled Mulder, not the other way around. He blamed Mulder for Deep Throat and Scully's deaths and said he was not going to let the same happen to him, hence he told Mulder to stop before he lead them to him.
When Mulder managed to catch up to the man he was pursuing, X came to Mulder's rescue but then brutally assaulted and executed the man. X later informed Mulder that the men who are involved in Scully's abduction would be searching his apartment for information they believed he had. X told him they believed he was out of town and this would be his only chance for justice, that waiting for these men and killing them was the only way. — One Breath
Mulder and Scully investigated a case involving the suicide of a US soldier that appeared to have connections to voodoo. They found themselves being stonewalled and X turned up to tell Mulder that the cases were being made to disappear and that the military was sanctioning Colonel Jacob Wharton's revenge for the suicides of two of his men. Men he believed were driven to it by Pierre Bauvais. He cynically advised Mulder that by the time they formed a committee to investigate it, the whole thing would have been made to disappear. — Fresh Bones
While Mulder was in pursuit of the truth about the alien clones, he went to X for information. X, however, was as reluctant as usual to tell him much. He did give him the location of the Alien Bounty Hunter's ship, and revealed that a unit is being sent to destroy it. Mulder insisted he get to this ship, X saliently pointed out to him he would not win the war if he doesn't learn to pick his battles, this being one he can't win. After finding an email from Mulder on his computer telling her he's gone and she can't follow, Scully put the X in the window. X turned up a while later and was surprised to find Scully there; he refused to help her, so Skinner and X had a violent confrontation where X pulled his gun on Skinner, but Skinner's assertion that by pulling the trigger he would be killing two men (the other being Mulder). Skinner then gave Scully the coordinates where Mulder had gone. — End Game
X used Mulder to find Dr. Banton (a physicist whose shadow had become lethal following a laboratory accident involving dark matter) and turned him over to the people he had been hiding from. — Soft Light
Mulder was following a lead to a train after an investigation into an alien autopsy video he bought from a magazine ad. Mulder believed the video to be genuine and managed to find out the location of the train car where the autopsy took place. X went to Scully to tell her that Mulder mustn't get on that train, and that he would be in danger if he did. Scully called Mulder to try and stop him, but he ignored her advice and jumped on the train anyway. When Scully pressed X for more information, X urged her to pursue the chip she took from her neck for answers. — Nisei Mulder discovered the autopsy car but ended up locked inside it with the Red-Haired Man who had killed several of the Japanese doctors that carried out the autopsy, including Dr. Shiro Zama. The Red-Haired Man revealed to Mulder that the car was rigged with a bomb on a countdown, and that they had an hour and forty two minutes to get the car to a deserted location and themselves to safety. X was able to arrive at the location of the train car. Thanks to some help from Scully, Mulder was able to unlock the exit door but was then brutally assaulted by the Red-Haired Man. As he went to make his exit, X shot him, dead, and saved Mulder's life by carrying him out of the train car as it exploded, at the cost of losing the alien hybrid/plague carrier. — 731
Mulder and Scully started investigating a case where previously stable people seemed to be suffering from some form of psychosis and ended up murdering innocent people they believed were someone else. Mulder found out about this case from an anonymous man who emailed him to meet but would not reveal who he was working for. He did however tell Mulder that if he didn't investigate this case more people would die. Mulder later discovered that X was involved. He killed the men who knew about the devices planted on people's television poles that caused them to exhibit such violent behavior. He also explained to Mulder that his orders were always to clean up the evidence, he was just hoping Mulder would get to the men first.
Mulder berated him for risking his and Scully's lives, but never his own. X simply smirked at him; Mulder was unaware of who actually saved him from the train car. When Mulder pulled his gun on X, X questioned Mulder by asking if this would be his victory, by killing X. He said, "The truth is, you need me, Agent Mulder." Later X met with Cigarette Smoking Man to let him know that all the evidence and people involved has been eliminated. X had killed the informant who tipped off Mulder, and lied by saying the source to Mulder's informant remained unknown. — Wetwired
The Death of XEdit
X was a known subordinate of the Cigarette Smoking Man, and followed him to the Mulder summer residence in Quonochontaug where he met Teena Mulder. X took several photographs. She collapsed after this meeting and when Mulder went to see her at the hospital, she wrote the word PALM. X presented the pictures he had taken of Cigarette Smoking Man and Mrs. Mulder to Mulder. He asked Mulder if he had known that his mother and Cigarette Smoking Man knew each other. Mulder hadn't known and was amazed his mother was at the summer house in the first place, she had sworn she'd never go back there after she divorced his father. In the photos Cigarette Smoking Man seemed to be asking Mrs. Mulder for something, something that she had kept at that house, Mulder was mystified as to what that could be.
Mulder went to the summer house and searched the place, he then realized that when his mother wrote palm she actually meant lamp. With this information he smashed a lamp and found the pointed weapon used to kill alien clones. X met up with Mulder in a parking lot and tried to get him to give him the weapon. Mulder refused and they fought each other, as Mulder walked away X told him he's dead. — Talitha Cumi
The First Elder had also obtained copies of X's photographs and presented them to the Smoking Man to prove that he had a traitor in his midst. While Mrs. Mulder was in a hospital following a stroke, the First Elder leaked information that was she was unprotected in hopes that the traitor would present this information to Mulder and reveal his identity. X indeed went to Mulder's apartment to inform him that his mother was in danger, but he found Scully instead. She tried to get information from him about the inventory Jeremiah Smith was making, but he insisted that she leave that alone and protect Mulder's mother.
Later, the Syndicate set a trap for X to eliminate him. They sent the Grey-Haired Man to Mulder's apartment to place the X on Mulder's window. When X arrived at Mulder's apartment, he realized too late that he had been tricked. X ran for the elevator, where the GHM shot him in the stomach. While bleeding profusely, X was able to crawl down the hallway back to Mulder's apartment and leave one last clue. In his own blood, X wrote "SRSG," which would point Mulder toward a new source of information. He then bled to death at Mulder's door. — Herrenvolk
A Helpful GhostEdit
After a year on the run, Mulder was arrested for the death of Knowle Rohrer. Mulder protested his innocence since Knowle Rohrer was a super soldier and could not be killed by conventional means. He was put on trial and when things looked dire and he needed a strong witness, Mulder was visited by the spirit of X in his cell. X was as cynical as ever and tried to tell Mulder that the men he hoped to expose were not afraid of him or what his trial might reveal, that they were too powerful for that. He said he died learning that, and so will Mulder. However, he gave Mulder the address of Marita Covarrubias. She was the kind of witness Skinner believed they needed to help Mulder. Prior to X' appearance, they had not been able to locate her. — The Truth
+ Season 2
- - The Host (1994) ... Mr. X (voice, uncredited)
- - Sleepless (1994) ... Mr. X
- - Ascension (1994) ... Mr. X
- - One Breath (1994) ... Mr. X
- - End Game (1995) ... Mr. X
- - Fresh Bones (1995) ... Mr. X
- - Soft Light (1995) ... Mr. X
+ Season 3
- - Nisei (1995) ... Mr. X
- - 731 (1995) ... Mr. X
- - Wetwired (1996) ... Mr. X
- - Talitha Cumi (1996) ... Mr. X
+ Season 4
- - Herrenvolk (1996) ... Mr. X
+ Season 5
- - Unusual Suspects (1997) ... Mr. X
+ Season 9
- - The Truth (2002) ... Mr. X)
In 2017 the novel X-Files: Origins: Agent of Chaos by Kami Garcia was released, revealing that X had been shadowing Mulder since he was 17 and that X's first name was actually Reginald.