A cunning thief is desperate to wreck the opening of a historic landmark -- and Nancy is his target! On Gramercy Park in New York City, the magnificent Van Hoogstraten mansion with its priceless collection of glass birds is about to open to the public. Nancy, Bess, and George are invited. When the centerpiece of the collection, a beautiful crystal bird, is stolen, Nancy gets on the case. From family members with motives to keep the house, to an antiques dealer with a personal grudge, suspects abound. Then Nancy goes to the family's abandoned camp in the Adirondack forest, and zeroes in on the truth. In a violent nighttime thunderstorm on a solitary lake, Nancy confronts the culprit.