Enlisting her island crafting friends as convention workers, Nancy thinks she can finally realize her dream of arranging a Nancy Drew fan convention at the elegant Grand Hotel on Mackinac Island.

Hiding her financial secrets, Nancy rationalizes the need for a few white lies on her angel investor application to acquire the needed financing. Securing the loan through what she thinks are anonymous investors, she puts all her efforts into the convention-much to her husband's dismay.

Ruffled by the unexpected arrival of the mysterious Mr. and Mrs. Mason and their overbearing entourage at the convention reception - she is especially perplexed when they reveal they are the angel investors who supplied her loan. Hoping to delight the convention attendees, the Masons bring a rare, first-edition of The Mystery at Lilac Inn in pristine condition for display. Chaos breaks out when the Mason's prized possession goes missing.

Can Nancy and her convention helpers use the lessons they've learned from the famous girl sleuth to counter the mounting insinuations pointing to their group as the thieves, or is Nancy holding back the truth about her real life and beliefs from everyone?