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.
A scheming woman seeks to kill her husband to collect the insurance money, and is willing to seduce anyone she can to do it - including her husband's brother.
Two aliens arrive on Earth trying to kill each other. This is not easy, since they seem to be able to regenerate lost body parts and survive bullet wounds. Both of them happen to meet a young pathologist Dori Caisson, and each alien tells her that he is a peacemaker (an intergalactic cop) and that the other one is a bad guy. Whom can she trust?
