Seven years later, Mulder returns to the FBI when the X-Files is re-opened, in order to look into a government conspiracy, when it transpires they have been using alien technology. Along with Scully, they investigate several cases together like they had done originally. Six weeks after their return to the X-Files, Mulder confronts an alive Smoking Man to try and prevent him carrying out a plan to depopulate the United States using a virus applied to smallpox vaccines. In a vision of Scully's, Mulder falls sick to the disease, but refuses the Smoking Man's help and his proposal to join his elite. Mulder is saved by Agent Miller and they regroup with Scully, however, she says Mulder needs a blood transfusion and only their son can give it to them. At that moment, an unidentified flying object hovers over the trio, which is where season ten ends. The beginning of season eleven reveals this vision came from Scully's son, William. Over the course of season eleven, Scully and Mulder search for William. Skinner learns from the Smoking Man, that the Smoking Man, who is Mulder's father, also artificially impregnated Scully, and thus is William's father as well. In the third episode of the eleventh season, "Plus One", Scully and Mulder are intimate again. In the season 11 finale, "My Struggle IV", she reveals to Mulder that she is pregnant with his child.