The story begins when Claudia Kincaid, an 11-year-old, decides to run away from home because she thinks her parents don't appreciate her. So she runs away to the Metropolitan Museum of Art in New York City. She asks her younger brother Jamie who is 9 to accompany her.
Much of the early part of the novel details how Claudia and Jamie settle in at the museum: blending in with school groups on field trips during the day to learn more about the museum's exhibits, hiding in the bathroom at closing time to avoid the staff checking to make sure that all the patrons have left the museum, bathing in the fountain, picking up "wishing coins", and sleeping on antique beds. During their stay, they become fascinated with the newest exhibit: a beautiful statue of an angel, suspected to have been crafted by Michelangelo. They research the statue, and discover that it was sold to the museum by a Mrs. Basil E. Frankweiler, who lives in Farmington, Connecticut. They spend the last of their dwindling money to travel to Mrs. Frankweiler's house, where they discover the angel's secret, hidden in the erratically organized files in Mrs. Frankweiler's office.
I LOVED this book! I don't know if it appealed so much because I lived in CT at the time, and visited the MET once a year. But I always imagined hiding inside the museum and coming out at night to explore. What an adventure!