When Brie was younger, her mama used to surprise her with treasure hunts around their island town. After she died three years ago, these became Brie's most cherished memories. Now, on her twelfth birthday, her mama has another surprise: a series of letters leading Brie on one last treasure hunt. The first letter guides Brie to a special place. The next urges her to unlock a secret. And the last letter will change her life forever.