A comet is due to pass by Earth and there is a widespread panic and distress like Armageddon, when it suddenly changes course and hurtles towards Earth. Comet does not crash but it slows down and lands in a lake in Pacific Northwest.

Over the course of 50 years, forty four hundred people vanish under mysterious circumstances and were presumed dead or missing. And, these 4400 people emerge from the comet - a ball of light.

These people were of different ages and from different walks of life and did not look even a day older than when were last seen. It seems that these people are unaltered and untouched by time.

It becomes apparent that many of them have developed special physical and psychic powers including Superman strength, healing touch and clairvoyance. The 4400 are eager to reunite with those they left behind.

The 4400 deals with what happened when these 4400 people are forced to deal with the challenges of living in present and also what does it mean for those who live with the returned people.

Homeland Society’s federal division agency called NTAC (National Threat Assessment Command) is formed to follow The 4400.