Luther must confront a demon from his past, as both the police and Cornelius converge on his home. With Halliday convinced that the body in the morgue isn't their killer, can Luther put his own troubles to one side and find the true murderer before he strikes again?

A new spate of nightmarish murders brings John Luther to once again face the depths of human depravity on the streets of London. As the body count rises, and gangster George Cornelius applies his own pressure, can Luther catch a killer and save his own neck?

After the mysterious drowning death of his successful brother Justin, Carl Dawson (Matthew Rhys) heads to London to investigate. Teaming up with his brothers beautiful girlfriend (Sienna Guillory), Carl discovers that Justin was leading a double life. As he continues to delve deeper into the heart of Londons wild, drug-crazed club scene, Carl is drawn into a seductive underground web of blackmail, deceit and possibly murder amidst a sea of forbidden...