Three years later it is revealed in "William", that he survived the gunshot, but was subjected to horribly disfiguring experiments at the hand of his father. Posing as Mulder, he infiltrated Scully's house, and injected William with a magnetite substance to seemingly "cure" the baby of his telekinetic powers. The motivation or repercussions of his actions are never fully explained. He testified for the defense during Mulder's murder trial in "The Truth". He also revealed during the trial that Teena Mulder was having an affair with the "Cigarette Smoking Man", and that he and Fox Mulder are half-brothers. A DNA test conducted on a disfigured Spender in the episode "William" initially led agents Scully, Doggett and Reyes to believe he was Mulder thus lending further credence to Spender's claim that both he and Mulder are the children of the "Cigarette Smoking Man".