When Detective Superintendent Cully returns to South Island for a long-awaited school reunion, little does he know that the event will swiftly turn into a nightmare. A devastating mass shooting unfolds, and Cully is thrust into the role of leading the investigation. However, amidst the chaos, he battles his own demons, fearing that past abusive behavior will resurface with deadly consequences. The victims, all connected to Cully's school days, include Sophie Cairns, a former classmate and his ex-girlfriend, who miraculously survives the tragedy. In her book, a trauma therapist boldly suggests that fatal violence is the only solution to unbearable agony. As the relentless police team hunts down the shooter, Cully's path intertwines with that of DC Indah Kasali, forging a close bond. Sophie and Indah find themselves entangled in a battle to win Cully's affections. South Island Slaughter is a gripping thriller that explores the harrowing aftermath of tragedy, the complexities of human relationships, and the haunting effects of a troubled past.