Last One Out by Jane Harper

THE DAZZLING NEW NOVEL FROM THE MASTER OF CRIME He had been here, that was clear from the marks in the dust. And he had been alone. In a dying town, Ro Crowley waits for her son on the evening of his 21st birthday. But Sam never comes home. His footprints in the dust of three abandoned houses offer the only clue to his final movements. One set in. One set out. Five long years later, Ro returns to Carralon Ridge for the annual memorial of Sam's disappearance.