On a leave of absence from the police force, Luther is laying low in a rundown cottage on the edge of England but a visit from his old colleagues at the Met brings a shocking piece of news that draws him back to London in search of the truth. Meanwhile, a gruesome serial killer has struck the city. With a trail of clues leading from one crime scene to the next, Schenk and his team must work out the twisted logic that connects each victim but this murdering mastermind is more than a match for the police, outsmarting them at every step. It's not long before Luther is back in the Bullpen, determined to steal a march on the killer before it’s too late.