Frank and Joe Hardy investigate when danger threatens Bayport's new self-defense school and find themselves up against a ruthless real-estate developer out to buy the building in which the school is located.
- ISBN10 0785750770
- ISBN13 9780785750772
- Publish Date 1 November 1990 (first published 1 January 1990)
- Publish Status Out of Print
- Out of Print 6 April 2021
- Imprint Turtleback Books
- Edition Turtleback School & Library ed.
- Format Hardcover (Library Binding)
- Language English