On 1 November 2012, the BBC Luther website and Facebook page announced the third series will consist of four episodes. Shooting started in November 2012. Sienna Guillory has been cast to play Luther’s new love interest. Further guest stars include Lucian Msamati and Ned Dennehy. The third series began airing on 2 July 2013.
John Luther is a Detective Chief Inspector (DCI) working for the Serious Crime Unit in season one, and the new Serious and Serial Crime Unit in season two. A dedicated police officer, Luther is obsessive, possessed, and sometimes dangerous in the violence of his fixations. But Luther has paid a heavy price for his dedication; he has never been able to prevent himself from being consumed by the darkness of the crimes with which he deals. For Luther, the job always comes first. His dedication is a curse and a blessing, both for him and those close to him.