Luther

The titular character in Luther (Idris Elba) is a detective with the London police with a single-minded focus on capturing serial killers and sexual predators. He has a genius-level investigative mind but lacks self-control when it comes to his own relationships and emotional life. His singular focus has damaged most of his personal relationships, and his identity straddles a terrifying line between the light of justice and the darkness of the criminals he pursues.