Neil Garvie can't move on from a thing he didn't do. He saw the boy. He knew he needed help. But all he could do was hide - and one of the world's most notorious serial killers got away. Years later, Neil has a successful career as a criminal psychiatrist, unpicking the very darkest of human behaviour. Because, despite what he saw that day, Neil knows there's no such thing as a monster. But now his father, John, has disappeared - and the evidence suggests he was investigating the very killer that still haunts Neil. Which means that to save his dad, Neil is going to have to stop hiding, and go back into the darkness. And this time, he might not make it back alive...