The girl emerged from the woods, barely alive. Her story was beyond belief. But it was true. Every dreadful word of it.

Days later, another desperate escapee is found - and a pattern is emerging. Pairs of victims are being abducted, imprisoned then faced with a terrible choice- kill or be killed.

Would you rather lose your life or lose your mind?

Detective Inspector Helen Grace has faced down her own demons on her rise to the top. As she leads the investigation to hunt down this unseen monster, she learns that it may be the survivors - living calling cards - who hold the key to the case.

And unless she succeeds, more innocents will die . . .