Chris Parker is a popular high school senior living in Oak Park, Illinois. When her boyfriend, Mike Todwell, cancels what was supposed to be a romantic anniversary dinner date at the last minute due to a family emergency, she reluctantly accepts a job to babysit eight-year-old Sara Anderson, who idolizes Thor and roller skates whenever she can. Her high school freshman brother, Brad, secretly fantasizes about Chris being his girlfriend, the two who only cordially say "hi" to each other in the school hallways, if that, when they run into each other. Chris' babysitting job takes a turn when her naive best friend, Brenda, who was planning on running away, frantically telephones from the bus station in downtown Chicago realizing the scariness of the situation, she needs a ride home as she has no money. As Chris has no money either to pay for a cab for Brenda, she, Brad, Sara, and Brad's best friend, Darryl Coopersmith, drives into the city in her mother's station wagon to pick up Brenda. While Brenda faces her own issues in waiting for Chris, she and her charges get into one misadventure after another having to do with, among other things, mechanical problems with the station wagon, a jealous husband with a philandering wife, a car theft ring, a blues club with an unofficial yet unbreakable policy, a gang war, a frat party, a cheating boyfriend, and an office party in an upper floor of a skyscraper. What happens is affected by Chris' need to mind the kids who want to go off on divergent directions, and the current issue of Playboy whose centerfold has an uncanny resemblance to a certain babysitter. The primary question becomes if Chris can get Brad, Sara, Darryl, and Brenda home in one piece before the Andersons get home and discover their adventurous night.