Two incompetent crooks attempt to break in and kidnap Tyler and Katie while the two girls are alone at Katie's house. But the girls have some tricks up their sleeves, and using a host of wily pranks and booby traps up their sleeves, they successfully escape to their secret playhouse. When the criminals finally do find the kids, they have to contend with two new foes -- pet pony Two-Bits and a horse named Pepper -- who come to the girls' rescue.