When notorious child abductor - known as The Marsh King - escapes from a maximum security prison, Helena immediately suspects that she and her two young daughters are in danger. No one, not even her husband, knows the truth about Helena's past: they don't know that she was born into captivity, that she had no contact with the outside world before the age of twelve - or that her father raised her to be a killer. And they don't know that The Marsh King can survive and hunt in the wilderness better than anyone... except, perhaps his own daughter.