Karen's mom has fallen in love with the veterinarian! The wedding is scheduled for the end of summer. But Karen generously offers her and Melanie's services to baby-sit Priscilla Clark, a six-year-old better known as Pistol. The little girl has broken both her arms in a skateboard accident, and her Grandmother just can't cope anymore. It's up to Karen and Melanie to keep Pistol occupied and out of trouble all summer. A letter from Karen's father arrives announcing he will pick up Karen to take her camping at Yellowstone with his current girlfriend. He has often failed to keep his promises and there's no date for the vacation. He could not come at all, or he might come when Karen wants to be at home for her mother's wedding.