It's Nina Landry's birthday, and she's supposed to have her kids ready to leave in a few hours for a Christmas holiday in Florida with her new boyfriend. But her 15-year-old daughter, Charlie, spent the night at a friend's and hasn't come home yet. Not by 10 a.m., not by 11.....

Nina is getting angry - they have a plane to catch, and Charlie hasn't even bothered to pack. As time passes, slower and slower by the minute, Nina becomes uneasy. Her anger gives way to worry, and that worry quickly builds into panic.

By 1 p.m., she's wondering if Charlie has run away or if something far worse happened. And why won't anyone - not the cops, not Charlie's friends, not Charlie's father - take her disappearance seriously?

As day turns to night at Nina's home on Sandling Island, 60 miles from London, a series of ominous secrets leads Nina from sickening suspicion to deadly certainty. The question becomes less whether she and her daughter will leave the island in time and more whether they'll ever leave it again.