4400 centers on the return of 4400 people who, previously presumed dead or reported missing, reappear on Earth. Though they have not aged physically, some of them seem to have deeper alterations ranging from superhuman strength to an unexplained healing touch. A government agency is formed to track the 4400 people after one of them commits a murder.
Season four continues the incredible story of the 4400. Old adversaries become new allies, and family ties are strained to the breaking point in the battle over promicin. Can the 4400 lead mankind into a new world, or will the forces working against them spell the end for their kind?