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.

A 4400 terrorist releases a signal at NTAC that makes the men violent, forcing a lockdown of the facility. Lilly questions how the Centre is handling her daughter, and Shawn tries to recruit a familiar face.

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.

Audrey Parker, an elderly woman, takes promicin and develops the ability to astral project. Meanwhile, Shawn decides to start publicly healing people again despite threats from the government to shut him down. And Ben and Maia return to Seattle to visit Diana.

Tom tracks Jordan to a small town, where he meets a woman who can relieve people's stress by talking to them. Meanwhile, Marco and Diana have a nice talk. Maia's visions are giving her nightmares.

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 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.

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.