The Grey-Haired Man (played by Morris Panych) was one of the Syndicate's hitmen. The man often attended Syndicate meetings.
IN 1995, the GHM went with two others to a diner to intimidate Walter Skinner into stopping his investigation into the ending of Melissa Scully's death investigation. It did not work. (TXF: "Piper Maru")
The following year, under the direction of C.G.B. Spender, the Grey-Haired Man and one of his associates who had accompanied him to the diner were involved in a plot to have the Assistant Director Skinner discredited and dismissed from the FBI. After using Skinner's credit card to hire a prostitute to approach Skinner and sleep with him, the GHM entered their hotel room and murdered her while the two slept, framing Skinner for the murder. The following evening, the GHM attempted to further incriminate him by stealing Skinner's car and running his wife Sharon Skinner off the road with it, but was identified as the assailant due to the facial imprint he left on the airbag when it deployed during the crash. The GHM and his accomplice would follow up by attempting to tie up any loose ends involved in the case: they first murdered the madam of the prostitute they'd hired to approach Skinner, and then tailed another prostitute who had witnessed her boss' interactions with the men. When agents Fox Mulder and Dana Scully used her as bait for the assassins, the GHM's partner was shot and killed causing the GHM himself to retreat from the incident and Skinner to be cleared of any wrongdoing. (TXF: "Avatar")
The GHM assassinated informant X to complete the trap laid by First Elder. (TXF: "Herrenvolk")
The GHM went to Betsy Hagopian's house to kill a hybrid clone Kurt Crawford using an alien stiletto. He also went to the Lombard Research Facility to find intruders. He found and attempted to shoot Fox Mulder after he had broken in with the help of The Lone Gunmen. A bullet-proof glass door allowed the agent to escape with the new information obtained from the facility's Crawford hybrids. (TXF: "Memento Mori")
On the CSM's order, he watched Skinner complete his work at the Desmond Police station. He killed Detective Ray Thomas with Skinner's gun (Sig Sauer P228) after Skinner left the station. Then, he drove the CSM to see Skinner later at the FBI. (TXF: "Zero Sum")