Aisling's two sons, Ethan and Finn, mean everything to her. Ever since becoming estranged from her own parents, though, she's always felt like a piece of her is missing. Desperate to find answers - about her family, and herself - Aisling uploads her DNA to an ancestry website, and is thrilled when it finds a match. But instead of finding answers, she comes face to face with a detective. Aisling's DNA is a match for a recent crime scene - the latest in a string of murders by a dangerous serial killer, known as 'the bonfire killer'. And the police have three lead suspects - her father, or one of her two sons. Aisling would do anything for her family - but can she protect a killer?