For decades, 4400 people who were overlooked by society vanished from Earth leaving no trace behind. Now, they have suddenly all returned to Detroit, Michigan without having aged a day and with no memory of what happened to them. The government is left trying to make sense of the phenomenon while analyzing any potential threats they pose.

Known as the 4400, the group of returnees must come to terms with their new reality, including some changes to themselves and the possibility that they were brought back at this time for a specific reason.