Emmett Barclay has a special relationship with his twin sister, Elizabeth. Together, they help solve some of London's most baffling homicides. For years, Emmett used his otherworldly connection to assist the London Metropolitan Police. That partnership came to an end when his last case nearly got him killed.
When a cryptic and taunting note addressed to Emmett is found on a brutally slain street person, he is suddenly reunited with his former police colleagues. Is it a challenge or a threat? Who would do this, and why? The answers seem more elusive than the killer himself.
As the death toll climbs, Emmett and the police are led on a frenzied hunt to find the vicious killer before more people die. When Emmett learns who the next victim will be, the murder investigation takes a terrifying turn.