From the Mixed-Up Files of Mrs. Basil E. Frankweiler by E.L. Konigsburg

From the Mixed-Up Files of Mrs. Basil E. Frankweiler is about 12-year-old Claudia and her 9-year-old brother, Jamie, who run away to live in the Metropolitan Museum of Art in New York City. While hiding out and learning about the museum's treasures, they become fascinated by a beautiful angel statue that may have been sculpted by Michelangelo. Their quest to uncover the statue's true origin leads them to the mysterious Mrs. Basil E. Frankweiler, who holds the key to the secret and who is narrating their story through her files