Mulder and Scully are sent to investigate the murder of a city official, which it seems no human could have committed. Meanwhile, Scully deals with a personal tragedy, which brings up many old feelings about the child she gave away for adoption

The investigations that Mulder and Scully previously began with conspiracy theorist and web-TV show host Tad O'Malley seem to have awakened powerful enemies. A widespread panic begins as people all over the country suddenly start falling gravely ill, and Scully must look within to try and find a cure. Meanwhile, Mulder confronts the man whom he believes to be behind it all, but another figure from Mulder and Scully's past may prove to be the key to their salvation.