Twelve years ago DI Monica Kennedy caught serial killer Pauline Tosh. Although Tosh never confessed to her crimes, she was convicted to life imprisonment. Monica moved onto her next investigation and never heard from her again. Until now; Tosh has sent Monica letter saying she has information, asking Monica to visit her at the remote Highlands Carselang prison. When Tosh hands Monica a hand drawn map with a cross marking the marsh lands near Inverness she knows she needs to investigate. The original investigation found Tosh guilty of four murders, but Monica was always convinced there were more victims and when a corpse is discovered it looks like the team have found a new victim on Tosh’s kill list. However, despite pressure to close the case Monica knows that nothing is that easy. As the team investigate connections between the victim and the renowned serial killer they discover something much more complex. When a series of arson attacks are compounded by leaks from someone close to the investigation Monica realises the case is anything but cold. As she’s drawn into a murderous past, a cold blooded killer watches, far too close to home for comfort.