The second season of Dexter premiered on September 30, 2007, and ended on December 16, 2007. "It's Alive", the season premiere, attracted 1.09 million viewers in the United States, making Dexter the first Showtime series to attract more than a million viewers with a season premiere. The season finale, "The British Invasion", attracted 1.4 million viewers, making it the program's most-watched episode until the airing of the season three finale, "Do You Take Dexter Morgan?". Including digital video recorder usage, season two was watched by an average of 2.4 million viewers on a weekly basis through 11 full weeks, outperforming season one by 21%. The season received universal acclaim from critics, and was praised as "one of the best shows on TV this decade" by the Chicago Sun-Times, while Variety considers Hall's portrayal of the title character as a "towering achievement, one that eclipses the show's other shortcomings and rough patches"; the aggregate site Metacritic scored the season at 85 out of 100 based on 11 reviews.
In the season, the bodies of Dexter's victims are uncovered and an investigation is launched in Dexter's own department to find the killer, dubbed the "Bay Harbor Butcher". During this time, Debra struggles to recover after surviving Ice Truck Killer's attempts to murder her, and Rita sends Dexter to Narcotics Anonymous meetings when she suspects that he has an addiction. Sergeant James Doakes, stalks Dexter, suspecting that he is connected with the "Ice Truck Killer" killings. Three new characters are introduced: Keith Carradine appears as Special Agent Frank Lundy, an FBI agent who heads the "Bay Harbor Butcher" investigation, JoBeth Williams as Rita's mother Gail, and Jaime Murray as Lila Tournay, Dexter's Narcotics Anonymous sponsor.