4400 people, assumed to be dead or missing over the past fifty years, reappear in a ball of light. None have any memory of where they've been, and some are manifesting paranormal abilities.

Tom and Diana investigate a 4400 who has used his ability of enhanced reflexes to become a vigilante.

Tom and Diana investigate Oliver Knox, a 4400 suspected of being a serial murderer.

NTAC races against the clock to stop a group of fanatics targeting 4400s.

Diana helps Tom break Kyle out of NTAC quarantine, eventually leading them to discover the truth behind the 4400.