Wayne Szalinski is back and this time his notorious shrink machine misfires again, and it is the adults who are shrunk. Believing their parents have left them home alone for the weekend, the kids take advantage of their newfound unsupervised freedom by filing up on junk food, Rollerblading in the house, playing loud music, and throwing a party for their friends. While desperately trying to get the kids to notice them, since they are only 1/2 of an inch tall, the adults are able to learn a few things about their kids.