The Forbidden Tower

The story tracks Kay Tracey as she uncovers a mystery involving an old fort and a restricted tower located on the property of Jasper Jackson, a mean neighbor living in Florida.
Once in Florida, Kay searches for Emily Dodd, who is missing, and investigates strange events at a nearby estate. The owner, Jasper Jackson, is unfriendly and hateful towards Mrs. Dodd, and Kay wonders if he might have something to do with Emily's disappearance.
This specific title was later dropped from reprint runs of the series, making original editions highly collectible for vintage juvenile fiction enthusiasts.