How many strings will fray before a family business falls apart?

Nancy, George, and Bess are going on a vacation to Paris, and Nancy's father pulled a few strings to get the girls some quaint accommodations: a tiny top-floor flat in a small three-story house on the Ile Saint Louis. The first floor of the building is a puppet theater, museum, and shop, owned by twenty-seven-year-old Mimi Loiseau, who lives on the second floor.

Mimi's great-grandmother had always hinted at a unique family treasure, but she died before she could tell Mimi what, or where, it was. Now someone is stealing puppets and vandalizing apartments. Could this someone be looking for the long-lost treasure? Nancy's on the scene just in time to help save Mimi's business—and to make sure they all get home in one piece!