This is book number 34 in the The Boxcar Children Mysteries series.
The Boxcar Children are spending their vacation on a farm. They learn to do everything from milking cows and making homemade jam to raising a barn. Then one day they spot a beautiful horse locked up in a stable. Who is the mystery horse? And why is it hidden?
The Boxcar Children Series was created by Gertrude Chandler Warner, a teacher, when she realized that there were few, if any, books for children that were both easy and fun to read. She drew on her own experiences in writing the mysteries. As a child, she had spent hours watching trains near her home, and often dreamed about what it would be like to live in a caboose or freight car. In each story, she chose a special setting and introduced unpredictable, unusual or eccentric characters, to help highlight the Aldens’ independence and resourcefulness. Miss Warner lived in Putnam, Massachusetts until her death in 1979.