It's spring break and the only assignment Wally Hatford and Caroline Malloy have is to do something that they have never done before. Wally's sure that will be a cinch once he hears the great news about the mighty Benson brothers coming to stay for vacation. It will be nonstop action all the way. For starters, the nine Benson and Hatford boys plan on scaring the three Malloy sisters silly by convincing them that their house is haunted. Of course, the boys don't know that the girls are hard at work plotting their own special surprise welcome. The Bensons don't know what they're up against with the Malloy girls. But they soon will. Meanwhile, everyone in town knows there's a hungry cougar on the prowl. When the kids decide to take a break from their tricks and join forces in catching the cougar, guess who gets stuck with the scariest job? This will surely be something no one has ever done before.