Once settled into the museum, Claudia and Jamie find themselves caught up in the mystery of an angel statue that the museum purchased at auction for a bargain price of $225. The statue is possibly an early work of the Renaissance master, Michelangelo, and therefore worth millions. Is it? Or isn't it? Claudia is determined to find out. Her quest leads her to Mrs. Basil E. Frankweiler, the remarkable old woman who sold the statue, and to some equally remarkable discoveries about herself.