When Ryan Kennedy is imprisoned for the murder of a police officer, he knows what he has to do. Keep his mouth shut about who he was working for, keep his head down, and rely on his youth to keep his sentence short. When he gets out, he'll be rewarded. Following the death in the line of duty of her colleague, DI Keiran Shaw, DS Sarah Collins has left the Met for a quieter life in the countryside. But when the mother of a missing teenager begs her for help, she finds herself drawn into a much bigger investigation, one that leads her right back to London, her ex-colleagues Lizzy Griffiths and Steve Bradshaw, and Ryan Kennedy, the kid who shot Kieran. The powerful fourth instalment of The Tower explores the devastation that organized drug-running gangs can wreak on young lives. It asks who deserves to be saved - and whether saving them is even possible...