Nine-year-old Caroline Markham visits the local art gallery -- and makes an extraordinary discovery. In one corner there is something even more compelling than the paintings. It's a sculpture of a girl named Nina with a cat named Sammy on her lap, sitting in a rocking chair. There is no Do Not Touch sign like on the paintings. And Caroline can actually push the chair back and forth, and pat Sammy. Then one day a sign is placed on...