On a cloudless summer day, ghostwriter Phyl Long and educator Virgie Campbell meet as they wait for a private boat to Castaway Island. The attraction between the two is immediate, as is the excitement of a relaxing weekend getting to know each other. But once they arrive on the island, Phyl and Virgie discover things aren't what they should be. After meeting the other guests, they realize the staff are confused, there's no Wi-Fi, and the phone coverage is spotty. And there's no way to leave the island.

A charged accusation. A death. Another death, and then another...and another... As their fellow island occupants are murdered one by one, Phyl and Virgie realize their only hope of escaping is to work together to unmask the killer. But how does each know that the other isn't using their budding romance as cover for a very twisted plan?