Seventeen-year-old Annie Tillery and her Aunt Jill set off for Long Island's Fire Island for a vacation of surf, sun, and sailing. Annie is happy to leave behind the stress of her relationship with her parents. Aunt Jill, who is an NYPD detective, is mixing her vacation with a case she must keep secret from Annie, who is suspicious nevertheless. Annie finds romance and intrigue when she meets Ty Egan, the nephew of their host on the island. They find themselves in the middle of an eerie adventure when she and Ty investigate the tragic and perplexing story of a local ghost.
Annie becomes increasingly uneasy and the investigation turns sinister when Aunt Jill goes missing, the ghost appears, and the troublesome neighbors in the cottage next door become hostile. When they find one of Aunt Jill's special earrings on the neighbor's porch, they begin to wonder what she was doing there. Will they find Aunt Jill before it's too late? In the breathless conclusion to their investigation, Annie and Ty narrowly escape death solving the mystery of "The Madonna Ghost."