The three unstoppable Ninja brothers fight to save their hero (Hulk Hogan) and Mega Mountain Amusement Park from the vicious kid-hating Medusa (Loni Anderson).

Young martial artists face their grandfather's foes when they accompany him to Japan to deliver a priceless dagger.

Each year, three brothers visit their grandfather for the summer. He is highly skilled in ninjutsu, and for years he has trained the boys in his techniques.