The fourth and final season of The 4400 ran from June 17, 2007, to September 16, 2007. Like the previous two seasons, it featured thirteen episodes, but there was no two-hour premiere. On December 18, 2007, it was announced that due to the ongoing Writers Guild of America strike, budgetary problems, and lower-than-anticipated ratings, The 4400 had been canceled and would not be returning for a fifth season, despite the fourth season's cliffhanger.
A woman can project herself astrally, remaining unseen, but her body is murdered during astral projection. She must find a way to contact Tom and Diana to catch her murderer.
Collier tries to persuade Shawn to join his movement. Meanwhile, a 4400 who knows the truth behind historic conspiracies goes missing, prompting a search by Tom and Diana.
Shawn Farrell's political ambitions are threatened by a woman who claims he healed her mother in return for sex. At the same time, Jordan Collier annexes part of Seattle itself and calls it "Promise City", threatening to retaliate if opposed.
Opposing sides all wake up inside NTAC without any memory of how they got there. A lockdown at NTAC traps everyone, including Collier and his group, and everyone must put aside their differences and work together in order to find a way out.
Richard surprises Isabelle when he shows up in Promise City... but the happy reunion takes a turn when Richard kidnaps her in hopes of starting a new life with his daughter. Meanwhile, Tess, her schizophrenia out of control, uses her ability to take control of people at a diner, forcing Kevin to call Shawn for help.
Tom has trouble focusing on the hunt for Richard Tyler because of dreams he's been having about the future. Richard, in hiding with Isabelle, is visited by his wife, Lily who has been dead for over a year. Meanwhile, Jordan Collier's movement is threatened when Shawn announces that he is working on a test with Kevin Burkhoff that would tell people whether or not they would die if they took a shot of promicin.
A computer virus attacks Ubient Software, owned by Drew Imroth — a suspected member of the Marked. Elsewhere, Maia visits Promise City and receives an unexpected birthday gift.
Meghan Doyle and Diana discover a way to extract the future entity out of Tom, which could cost him his life. Meanwhile, Shawn recruits a small band of promicin positives to bust Kevin out of Promise City. Isabelle delivers Jordan Collier into the hands of The Marked.
Seattle falls into chaos and NTAC is forced to look to Promise City for help. Meanwhile, Isabelle is ordered to murder Kyle Baldwin and Jordan attempts to escape from The Marked.
