A drama about a group of doctors and those around him suffering from conflict and agony in the middle of a mysteriously spreading disease, try to solve what is causing the mysterious illness before thousands of people die. Kang Joo Hun is director in charge of the disease's epidemiology or epidemiological investigator. He is a former officer from the military police who has natural born insight and is at risk of losing his loved one to the virus. Lee Na Hyun is his lover who is taken by the virus when it's out.