Harold Piller
Harold Piller (played by Anthony Heald) claimed to be a psychic who assisted in police investigations.
Piller had done thorough research into his power and was known to have assisted in the search for missing children's bodies in Kashmir, India following a horrific train accident. He also had a history of mental illness and schizophrenia. Piller lost his son suddenly one night after having a brief vision of him dead. The police did not believe him, but evidence did not contradict him either.
In 2000, Piller came to Fox Mulder and Dana Scully to help with the disappearance of Amber Lynn LaPierre. Neglecting to tell them his medical history and that he was under investigation for his son's death, he proceeded to relay what little information he was able to glean. Mulder gave Piller more credence than Scully and allowed him to participate in the investigation, during which Piller sensed a connection between the LaPierre case and Samantha Mulder. One night, Piller demanded Mulder's attention and claimed that his mother was present and needed to convey something to Mulder. Mulder began to lose faith in Piller, as the experience ended abruptly, but discovered that he had somehow written down "April Base" without even knowing it. Mulder and Piller went to the Air Force base and eventually found the house where Samantha lived while a subject of the Project with Jeffrey Spender. The two left, and Piller convinced both Mulder and Scully to go back. There, in the house, Piller attempted to "summon" people there. Mulder found Samantha's journal.
The three then went to the home of Arbutus Ray, a nurse who admitted Samantha after she ran away. Piller was surprised that Ray had corroborated the details of children taken by walk-ins. Unbeknownst to Piller, Mulder had encountered the spirit of not only Samantha but also his son. Mulder tried to convince Piller that the children were dead, but safe also and that he should just let go, but Piller could not. He went into the forest where Mulder was to try to see his son. (TXF: "Closure")