Hobby Horse Hill by Lavinia Davis, T141, 7th Scholastic paperback printing, 1966, 252 pages. Illustrated by Charles Beck.
DESCRIPTION: “Terry wasn’t at all sure she was going to like the Wades and Hobby Horse Hill, since her arrival was overshadowed by that of Cassandra, the beautiful chestnut mare.
All the Wade children could think about was horses. Terry soon caught their excitement, helped plan a circus to raise money for a new saddle, and rode in the horse show.
And when Cassandra disappeared, Terry did some super-sleuthing.” (from the back cover)