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.

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

Tom and Diana investigate a 4400 junior high school teacher accused of child abuse.

Tom finds himself in a world where the 4400 never happened.

A 4400 with the ability to repair damaged chromosomes hides a shocking past. And while Richard seeks out a tormentor among his Korean War buddies, Shawn reconnects with his family and tries to help Kyle.

Tom and Diana are drugged with a hallucinogen, that was created from oil that was secreted from the hands of a 4400.

Tom and Diana's investigation into a series of gruesome murders leads them to uncover another conspiracy within the government. At the 4400 Center, Shawn receives a gift from another returnee that allows him to see his future.

NTAC and the 4400 Center work together to find Jordan Collier. Kyle Baldwin gets a surprising visitor at the state prison.

A high school student develops an ability after injecting promicin. Tom visits Isabelle in jail, while Diana searches for her missing sister. Following the advice of a young woman, named Cassie, Kyle is able to wake Shawn from his coma. Jordan Collier's conscience gets to him. Meanwhile, NTAC gets a new director.

Tom and Diana search for someone who has the ability to make people's worst fears come true. Danny seeks Shawn's help to find a promicin shot. Meanwhile, Cassie leads Kyle to a book that contains a prophecy about Jordan Collier.

Meghan and Diana learn how to remove the entity from Tom, but the procedure is dangerous.

Meanwhile, Shawn finds help in his attempt to rescue Kevin from Promise City; and Jordan is betrayed by someone close.

Paramedics try to resuscitate Susan Farrell. They believe that she took promicin and lost the 50/50 lotto that comes with it. Danny is certain that she did not take the shot. After arriving at the hospital with the paramedics, things get complicated as everyone around Danny start to die. Garrity and another NTAC agent are sent to the hospital to assess the situation.