 A taxi picks up a middle-aged man standing out in the rain. Once in the cab, the man begins ranting semi-coherently and coughing up blood, so the driver takes him to an emergency room. Soon after checking in, two men claiming to be from the CDC say that the patient is infected with a highly dangerous pathogen and must be taken away, but the man has already escaped with the taxi driver. Frank and Lt. Gebelhouse are asked by the CDC to assist in tracking then pair down before they can infect anyone else. In the course of catching the two, Frank comes in contact with Patient Zero s blood, exposing him to whatever disease the man is infected with. What Frank learns when the bloodstain is examined will reveal that a much larger conspiracy is taking place.