The hunt is on for a shadowy killer after Maia has a vision of Jordan Collier's impending demise; Tom's personal life is disrupted by Kyle's frightening blackouts; Lily's reunion with her daughter Heidi irritates little Isabelle; Shawn offers sanctuary to a street urchin; and NTAC demands that Diana hand over Maia's diary.

Tom is startled when he awakens in an alternate world in which he's married to a new wife and Kyle is a well-adjusted medical student. Most jolting of all is his discovery that the 4400 don't exist there.

Tom and Diana pursue a 4400 who released a plague that eradicated a town's entire population and has powers that threaten to wipe out humanity. Also: a lobbyist from Washington, D.C., joins the 4400 Center to bring some political muscle to the movement.