Brothers, Zack and Woody (portrayed by real-life brothers Chris and Pat Petersen) are young karate students who embark on a weekend camping trip with their grandfather J.J. (Charles Lane). Along the way they meet a new friend, Carol Forbinger (Sally Boyden) and her parents (Rick Lenz and Sharon Clark). When the Forbinger family encounters a tough-talking backwoods mother (Ann Sothern) and her two bumbling sons (Joe Spinell and John Davis Chandler) who decide to hold Carol captive believing they can collect a sizeable ransom, the karate kids must find a way to use their martial arts skills to rescue the Forbinger girl with a little help from their grandfather and some new friends they meet along the way.