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

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

Tom and Diana investigate a mysterious structure being built at a psychiatric hospital, based on the drawings of one of their patients who's a 4400.

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

After living for 8 years in an alternate world that only Tom and Alana remember the world with the 4400 has returned as it was at the second the 8 years started. A 30 year old 4400 woman wakes up and finds everybody else in her local community dead. Maia puts April's love for her to a test.

NTAC is keen to find Jordan Collier's killer as Tom is desperate to find Kyle.

When 4400s around the world come down with life-threatening illnesses, Ryland comes back to NTAC and orders the sick - and even unaffected 4400s - to be quarantined. Tom and Diana race to find a cure and discover a shocking secret in the process.

Tom is accused of murdering TJ Kim. 17 year old Boyd Gelder has the ability to change his appearance whenever he chooses. Meanwhile, Shawn and Isabelle grow closer.

Isabelle seeks revenge on the Nova Group after they attack Shawn. Alana confronts the man responsible for killing her husband and son in a car accident nine years ago.

Kevin is on the run after horribly mutating due to the promicin experiments. Tom and Diana go to Tess for help. Diana gets what she believes is the flu and discovers something startling.

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

Tom and Diana continue their investigation on Jordan Collier's plan for mankind. Dennis Ryland rejoins NTAC. Isabelle prepares for battle.

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.

Diana locates her sister, April, who took promicin and developed an ability that puts her life in jeopardy.

Jordan wants Shawn to rejoin the movement. Meanwhile, a 4400 with an amazing ability disappears.

Tom, Diana, Jordan, Shawn, Kyle, Isabelle, Maia, Meghan, Marco, PJ and Brady all wake up inside NTAC without any memory of how they got there.

Tom has trouble focusing on the hunt for Richard Tyler because of dreams he's having about the future.

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.