During the past century, thousands of people have gone missing. When 4400 of them return all at once unharmed and looking the same as when they disappeared, the government investigates, unsure of how this can be possible. What the government does not know is that the presence of these 4400 will change the human race in many unexpected ways.

Over one year ago, thousands of missing people returned. Slowly, they begin to manifest strange powers - to heal and to destroy, to alter the present and to perceive the future. As it becomes clear that their gifts could reshape the world, the struggle for control begins. Who will decide the fate of humanity?

The third season continues exploring the travails of the 4400 people who all at once returned in a ball of light to Earth; though the returnees had not aged physically, many of them reappeared with dramatic abilities ranging from enhanced reflexes to precognition.

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?