Mulder and Scully have 24 hours to save A.D. Skinner from being killed by a biologically engineered disease. The disease appears to be created by a shadowy government organization, but in order to save Skinner's life they must determine who wants him dead and why. With Skinner's condition worsening, Mulder seeks assistance from Senator Matheson, who he hopes can provide some answers and help him to find a cure.