The fourth season of Dexter premiered on September 27, 2009, and concluded on December 13, 2009. The series was renewed for a fourth and fifth season in October 2008, with each season consisting of 12 episodes. The show's writers convened during February and March 2009 to brainstorm ideas for the fourth season, and filming was scheduled to begin in June 2009. In May 2009, Showtime announced that John Lithgow would guest star in all 12 episodes as Miami's latest and deadliest serial killer, and Keith Carradine would return as Lundy. The fourth season focuses on Dexter attempting to find his way to balance his family life, the birth of his son, and his "extra-curricular" activities.

Dexter Morgan is a fictional character introduced as the antihero protagonist of the Dexter book series written by Jeff Lindsay, as well as the television series of the same name. In the television series, Dexter is portrayed by Michael C. Hall.