Wayne Szalinski's notorious shrink machine misfires...again! This time, it's Wayne and his wife, brother and sister-in-law who are shrunk to just half an inch tall, forcing them to navigate through Wayne's home while trying to get their kids' attention. But thinking that their parents have left them home alone for the weekend, the kids take full advantage of their newfound unsupervised freedom, filling up on junk food, rollerblading in the house, playing loud music and throwing a party for their friends. None of it goes unnoticed though, as the adults gain new, respectful insights about them. And when the kids finally find the adults, they consider leaving them as is, but decide they want their parents just the way they've always been.