After a 7 month suspension, DCI John Luther returns to duty. With the assistance of DS Justin Ripley, he investigates a home invasion that resulted in the murders of Douglas and Laura Morgan who were found by their daughter Alice. After questioning her, Luther is convinced that she killed her parents and as much as tells her so. He has no physical evidence however and the police have not been able to find the gun. Alice is highly intelligent and is quite prepared to play psychological games with him. Luther meanwhile tries to repair his relationship with his wife Zoe from who he has been separated. She has met someone and has begun a new relationship news that doesn't go down very well.