Sách nói: Secret of Casa Grande

While visiting their friend, Florence, at her home in Mexico, Jo Ann and Peggy noticed a barred window which has no opening into any of the rooms of an ancient adobe house. Curious to find out what it is, the girls tried to investigate but no one seems eager to help them. Undaunted, the girls made plans to get there only to encounter dangers and find a thrilling discovery. - Summary by Mary Escano