Harry Bosch is facing the end of the line. Hes been put on the DROP - Deferred Retirement Option Plan - and given three years before his retirement is enforced. Seeing the end of the mission coming, hes anxious for cases. He doesnt have to wait long. First a cold case gets a DNA hit for a rape and murder which points the finger at a 29-year-old convicted rapist who was only eight at the time of the murder. Then a city councilmans son is found dead - fallen or pushed from a hotel window - and he insists on Bosch taking the case despite the two mens history of enmity. The cases are unrelated but they twist around each other like the double helix of a DNA strand. One leads to the discovery of a killer operating in the city for as many as three decades the other to a deep political conspiracy that reached back into the dark history of the police department.