Sue Ellen Crandell (Christina Applegate) is a 17-year-old high school graduate who, due to a lack of funds, cannot go to Europe for the summer with her friends. She is about to head to college in the fall. However, when her divorced mother goes on a vacation to Australia with her boyfriend, Sue Ellen looks forward to an entire summer of freedom with her siblings: 16-year old slacker/stoner Kenny (Keith Coogan), 14-year-old ladies' man Zach (Christopher Pettiet), 13-year-old tomboy Melissa (Danielle Harris), and 11-year-old TV fanatic Walter (Robert Hy Gorman). Much to Sue Ellen's dismay, her mother hires a live-in babysitter, Mrs. Sturak, a seemingly sweet, humble old woman who assures Mrs. Crandell that she can take care of all five children. As soon as Mrs. Crandell leaves, Mrs. Sturak shows her true colors as an evil tyrant, quickly drawing the ire of the children. However, she later dies of a heart attack. When her body is discovered by Sue Ellen, the children agree to stuff the babysitter in a trunk and drop her off at a local funeral home and keep her car. They discover that the envelope given to Mrs. Sturak by their mother with their summer money is empty; she had it on her when they delivered her body to the funeral home.