When Nancy Drew learns that she has won a holiday for two on an island resort, she is completely mystified because she had never entered any contest for such a prize. Her suspicions grow when an abandoned boat linked mysteriously to her and her father is traced to strangers at the same resort!
More than ever, Nancy realizes she must contact her girlfriends, Bess Marvin and George Fayne, who have gone to the island ahead of her. But unable to reach them, the young detective finds herself on the brink of yet another intriguing mystery involving a strange old medallion and a long lost treasure.