Almost everybody who has grown up in Chicago knows about the Thorne Rooms. Housed deep inside the Chicago Art Institute, they are a collection of 68 exquisitely crafted miniature rooms. Each room is set in a different historic period, and every detail is perfect. Some might even say, the rooms are But what if on a field trip, you discovered a key that allowed you to shrink so that you could sneak inside and explore the rooms' secrets? What if you discovered that others had done so before you? . . . And that someone had left something important behind? Eleven-year-olds Jack and Ruthie are about to find out!