From the Mixed up Files of Mrs. Basil E Frankweiler

When Claudia decided to run away, she planned the perfect escape. Because she needs money, she invites her penny-pinching younger brother Jamie to come along. And because she enjoys living comfortably, she chooses the elegant Metropolitan Museum of Art in New York City as their hideaway. While camping out in the treasure-filled rooms of the museum, they'll dodge night watchmen, sleep in a royal bed, and take baths in the public fountain. Claudia and Jamie discover something new every day, but the most fascinating thing of all is a small marble statue named Angel.