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.
As Detective Inspector Helen Grace 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 . . .