A new spate of nightmarish murders brings DCI John Luther to once again face the depths of human depravity on the streets of London. While the monstrous and seemingly indiscriminate killings become ever more audacious and public, Luther and new recruit D.S. Catherine Halliday are confounded by a complex tangle of leads and misdirection that seems designed to protect an untouchable corruption. As the body count rises, and gangster George Cornelius applies his own pressure, can Luther catch a killer and save his own neck?

With his friend in peril and a young woman kidnapped by the relentless serial killer, can Luther protect the innocent while preventing Cornelius' violent revenge from consuming him? Who is Luther willing to save, and who can't he bear to lose?