She surfaced from the depths of the sea… and was terrifyingly, inexplicably alone

Briana Devon knows her twin sister would never deliberately leave her — but when she emerges from underwater, Daria and their boat have vanished. Fighting rough waves and a fast-approaching storm, Bree doesn't have time to question:

if she wants to survive, she has to swim.

Exhausted and terrified, Bree barely makes it to a tiny barrier island, where Cole De Roca, who has also taken shelter, revives her. Bound to Cole by the harrowing experience, she turns to him as she struggles to understand what happened to her sister. What was her twin, whom she thought she knew so well, hiding? What really transpired that terrible afternoon? And what secrets lie dormant…below the surface?