A mother’s life is shattered in an instant when a speeding car runs down her five-year-old son. In I Let You Go, by Clare Mackintosh, the story alternates between the police search for the driver and the stunned and heartbroken Jenna. She leaves everything behind as she escapes to a remote Welsh town by the sea. Haunted by nightmares of the accident, Jenna is overwhelmed by guilt and grief. The police hunt for the killer but are frustrated by the lack of evidence and witnesses. The author, who spent 12 years as a police inspector, ably shows the grinding details and tedium of an investigation, but her real strength lies in the psychological depth she gives to Clare, and her faultless depiction of a mother’s unrelenting grief. The mystery rushes on, with sensational plot turns and ever-increasing tension, reaching a satisfying conclusion with a hint of menace.