On a warm evening in 1990, a young woman expecting a child meets a horrific end as she is buried alive in the sand, left to be overtaken by the rising tide. A quarter of a century later, this gruesome crime remains a mystery. Olivia Rönning, a student at the Police Academy, is assigned to delve into this cold case as part of her studies. Her interest in the case intensifies when she learns that her father was involved in the original investigation. Determined to uncover the truth, Olivia realizes she needs to track down the lead investigator, detective Tom Stilton, who has seemingly vanished without a trace.