Nantucket writer Madeline King has a new novel coming out and it's got bestseller potential. But Madeline is terrified, because in her desperation to revive her career, she's done something reckless: reveal the truth behind an actual affair involving her best friend, Grace. And that's not the only strain on Madeline and Grace's friendship: one fateful night, the two women argue, voicing jealousies and resentments that have built for 20 years. Bereft of each other, they get caught in the snares of a mysterious and destructive stranger.