- "When you're on enemy turf you'd better be ready to hold your ground!"
- — Tagline, from the front cover
The Hardys pay a visit to Bayport's newest martial arts school and find that someone's trying to run the place out of the neighborhood. The Scorpions, a tough street gang, say the building is on their turf, and the school's students have already felt the Scorpion's sting.
The home boys may want to rumble with the Hardy boys, but when high explosives come into the picture, Frank and Joe figure there's more than a street fight at stake. The unknown enemy is willing to use deadly force to destroy the school, and the Hardys will have to get down to business -- and give a lesson of their own.