Alice Lang was wearing her favourite scarlet dress when she disappeared 25 years ago, and her memory still casts a long shadow.

The past was like water. Once the tide turned, you couldn't hold it back.

In the long, hot summer of 1995, 22-year-old Alice Lang rents a caravan on a holiday park on the outskirts of the lively holiday resort of Severn Sands. She befriends Marnie, a shy, damaged little girl whose father is the park's caretaker and whose mother died a few months earlier. Will, whose mother runs the bar, falls in love with Alice and is unbearably jealous of anyone else she sees. Tensions rise until one evening Alice disappears from her caravan. She's never seen again, and only her scarlet dress is found washed up on the shore.

A quarter of a century later, the town is run-down, and nobody comes there anymore. Mr and Mrs deVillars, former owners of the holiday park, have passed the failing business onto their son, Guy, who promptly sells the land for development. Builders clearing the land to create an expanse of executive homes uncover human bones. It has to be Alice.

Will and Marnie’s lives were entirely shaped by what happened that summer, and now that Alice has been found, they must struggle to pin down their memories, to escape the secrets of the past, the lies they told and the unbearable guilt they're both carrying.

They need to find out what happened to Alice. Who killed her? And why?