A young pregnant woman is buried in the sand, slowly being submerged by the tide. 25 years later, the sadistic murder remains unsolved. Olivia Rönning at the Police Academy studies the case as a cold case exercise. Olivia becomes almost obsessed with the murder when she discovers that her father worked on the investigation. She quickly realises that she needs to find the lead investigator, detective Tom Stilton, but he has gone to ground.