Claire is only seven years old when her college-age sister, Alison, disappears on the last night of their family vacation at a resort on the Caribbean island of Saint X. Several days later, Alison’s body is found in a remote spot on a nearby cay and two local men – employees at the resort – are arrested. But the evidence is slim, the timeline against it and the men are soon released. The story turns into national tabloid news, a lurid mystery that will go unsolved. Years later, Claire is living and working in New York City when a brief but fateful encounter brings her together with Clive Richardson, one of the men originally suspected of murdering her sister. It is a moment that sets Claire on an obsessive pursuit of the truth – not only to find out what happened the night of Alison’s death but to answer the elusive question: Who exactly was her sister? As Claire doggedly shadows Clive, waiting for the slip that will reveal the truth, an unlikely attachment develops between the: two people whose lives were forever marked by the same tragedy.