Twin sisters Iris and Summer are startlingly alike, but beyond what the eye can see lies a darkness that sets them apart. Cynical and insecure, Iris has long been envious of Summer's seemingly never-ending good fortune, including her perfect husband Adam. Called to Thailand to help her sister sail the family yacht to the Seychelles, Iris nurtures her own secret hopes for what might happen on the journey. But when she unexpectedly finds herself alone in the middle of the Indian Ocean, everything changes. When she makes it to land, Iris allows herself to be swept up by Adam, who assumes that she is Summer.