Tom and Diana investigate a 4400 whose ability to increase the human bodies' metabolism just may be this weight-conscious world's answer to the ultimate fat-burner.

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

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.

Discovering that NTAC is behind the disease plaguing the 4400s, Tom and Diana try to get to the bottom of NTAC's cover-up, while Kyle considers turning himself in.

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.

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.

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.

Jordan Collier's movement takes a huge step forward when his followers settle in the heart of Seattle.

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

Tom and Diana must race to find the source of a computer virus that could bring down Ubient software, one of the world's largest software companies that is run by suspected member of the marked, Drew Imroth. Meanwhile, Maia visits Promise City where she receives an unexpected birthday surprise: a visit from her birth parents.

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.

Richard must protect his family when he and Lily are discovered to be 4400s.

A returnee exhibiting telepathic abilities seeks help from NTAC, but is instead used as a mole to infiltrate Jordan Collier's 4400 Center.

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.

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

Tom and Diana investigate Oliver Knox, a 4400 suspected of being a serial murderer.

NTAC races against the clock to stop a group of fanatics targeting 4400s.

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

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.

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

With the help of Dennis Ryland, NTAC track down the remining members of the NOVA group. Nikki pays Shawn a visit.

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.

NOVA group members that were in the custody of NTAC escape from jail with outside help from Jordan Collier. Diana tells April about her relationship with Ben. Shawn and Richard learn that Isabelle is working with Dennis Ryland.