DI Alec McKay is back. Twenty years ago, Jackie Galloway was a senior cop with a bad reputation. Then, he ended up on the wrong side of the wrong people, and his career was ruined. Sacked and with no pension, he ends up eking out his last days on Scotland's Black Isle, his mind lost to dementia, supported only by his wife, Bridie... until Galloway is found dead. The police assume the death to be accidental until Bridie reveals that her husband has been receiving threatening letters containing only the phrase: 'NOT FORGOTTEN. NOT FORGIVEN.' DI Alec McKay is struggling to come to terms with life without his estranged wife Chrissie, and is living in isolation on the Black Isle. As a junior officer, McKay had been allocated to Galloway's team and has bad memories of the man and his methods. Now he finds himself investigating Galloway's death. But when suspicion falls on him and more police officers are murdered, the pressure is on for McKay to solve the case. Why would the killer seek revenge twenty years after Galloway left the force?
