Bernard Gauthier was a French diver.
Gauthier participated in a mission on the Piper Maru to the North Pacific to retrieve a ship. When he reached it in his diving suit, however, he was shocked to find a person inside alive. Somehow, an oil left the man and into Gauthier. Unresponsive, the crew pulled him up. Gauthier, now infected with the black oil, convinced the crew he was fine and got out of the suit.
Under the influence of the oil, Gauthier caused radiation burns on the rest of the crew, piloted the ship back to San Diego, and pretended not to know anything to Doctor Seizer. He was discharged and went to his home in San Francisco Heights. He looked for a letter from the salvage company when his wife interrupted him. Instead of answering her, he chased her, held her down, and put the oil into her.
He woke up later, disoriented and covered with oil. Agent Fox Mulder arrived at the house looking for him, but Gauthier could not remember anything that happened since he was in the ocean. However, when Mulder mentioned the salvage company, he asked for the French consulate. (TXF: "Piper Maru")