Clare Riordan and her son Mikey are abducted from Clapham Common early one morning. Hours later, the boy is found wandering disorientated. Soon after, a pack of Clare's blood is left on a doorstep in the heart of the City of London. Alice Quentin is brought in to help the traumatised child uncover his memories - which might lead them to his mother's captors. But she swiftly realises Clare is not the first victim - nor will she be the last. The killers are driven by a desire for revenge - and in the end, it will all come down to blood.