Still reeling from the violent death of his partner Ripley, John Luther has left the police force and retired to a remote clifftop. After enduring so much tragedy, he has little left to live for. So when Luther finds out the one person he still loves might be dead, he has one aim, find whoever's responsible and make them pay. Meanwhile, DCI Theo Bloom and DS Emma Lane are tracing a gruesome chain of murders back to its source. A feral killer is devouring his victims and assuming their identities before moving on to fresh prey.
But the closer the police come to the black heart of this case, the more the truth becomes obscured; they are fumbling blindly in the dark, stumbling into a deadly trap. As the murderer's bloody mission gains pace, Luther realises he must intervene. Only he can immerse himself in the killer's complex psychosis and anticipate his next move. But John has personal business to take care of too, and his uncompromising approach leads him into trouble with a North London crime boss, the kind of trouble he's unlikely to make it out of alive. Then, when an inscrutable stranger turns up claiming to have a message from the dead, Luther is forced to confront the shadows of his past. Who is she? And how does she know his most deeply hidden secrets? Luther's problems are stacking up, and in order to solve them he will need to compromise his moral code once more. This is his most chilling case, a test that will push him closer to the edge than he's ever been before.