Don't trust your friends. Don't trust your family. Don't trust yourself....
When a young mother is found dead in her home with mysterious symbols drawn on her body, DI Katie Rhodes is shaken to her core; something is telling her that the clues link back to her old partner, Nathan Radley.
Formerly one of the best criminal psychologists on the police force, Nathan was renowned for getting deep into the minds of the murderers he hunted. But for the past year he has lived in isolation, terrified of losing control over his own dark desires.... Katie swore she'd never knock on Nathan's door again, but when another woman's body is found, she knows she doesn't have a choice.
As the body count rises and the calling cards get increasingly personal, Katie and Nathan realise that someone very close to them is playing a dangerous game. Who can they trust, and how many more innocent lives will be taken before they can crack this disturbing riddle?