How can you spot a murderer? Leo Stone is a ruthless killer - or the victim of a miscarriage of justice. A year ago, he was convicted of murder and sentenced to life in prison. But now he's free, and according to him, he's innocent. DS Maeve Kerrigan and DI Josh Derwent are determined to put Stone back behind bars where he belongs, but the more Maeve finds out, the less convinced she is of his guilt. Then another woman disappears in similar circumstances. Is there a copycat killer, or have they been wrong about Stone from the start?