After her boyfriend Mike cancels their anniversary date, seventeen-year-old Chris Parker invites her friend Brenda over to her Oak Park, Illinois, house to cheer her up, but is convinced by her mother to babysit the Andersons’ daughter, 8-year-old Sara, while they attend a party in downtown Chicago. Fifteen-year-old Brad Anderson is supposed to go to his friend Daryl Coopersmith’s house to spend the night, but he changes his mind when he finds that Chris is the sitter. After receiving a frantic phone call from Brenda, who ran away to the bus station downtown, Chris plans to go alone to pick her up but is coerced by Brad, Sara, and Daryl to take them with her. On the freeway, their station wagon suffers a flat tire and they are picked up by a tow truck driver, “Handsome” John Pruitt, who offers to pay for the tire when Chris realizes she left her purse at the Andersons’. En route, Pruitt gets a call from his boss Dawson with evidence that his wife is cheating on him, and he rushes to his house to confront the infidelity; Chris’s mother’s car is damaged when Pruitt accidentally shoots out the windshield while aiming to kill his wife’s lover with his snubnosed revolver. Chris and the kids hide in the adulterer’s Cadillac, which is then car-jacked by a thief named Joe Gipp.
Reaching their hideout in the South Side, the kids realize they have stumbled upon a chop shop, and Joe is chided by Graydon, the operation’s second-in-command, for bringing witnesses. They are detained in an upstairs office but escape. They enter a blues club where the band on stage won’t let them leave until they sing the blues. Chris, Brad, Sara, and Daryl recount their events that night to the audience and are allowed to leave, just as Graydon, Gipp, and their boss Bleak catch up.
Brad tells Chris about his feelings toward her but finds they are not reciprocated. After separating Daryl from a streetwalker who is a runaway, Chris is reminded of Brenda. They are found and chased again by Greydon and Bleak but escape on the Chicago “L” train and wind up in the middle of a gang fight. Brad is injured when one of the gang leaders throws a switchblade onto his foot. They take Brad to the university hospital, where he receives a stitch. They run into Pruitt, who is now on the run for his earlier attacks; he tells the kids he replaced the windshield, but Dawson wants $50 for the tire. The kids come across a fraternity house party, and Chris becomes attracted to Dan Lynch, a gentleman who learns of Chris’ problem and donates $45. He takes them to Dawson’s Garage and drops them off.
When they find Dawson, his blond hair and sledge hammer lead Sara to believe he is her hero Thor. He denies them their car because of the $5 shortage, but when Sara offers him her toy Thor helmet, he changes his mind and lets them go. Meanwhile, Joe Gipp tells Bleak about their troubles, and the three are waiting to follow them. The kids find the restaurant where Mike was supposed to take Chris and discover he is there with another girl. Sara slips away to look at a toy store while Chris yells at Mike. Brad stands up for his friend while Daryl kicks Mike into a food cart, ruining the dinner. Bleak spots Sara, and Graydon chases her to an office building where she hides; the others note her disappearance and follow, accidentally coming across the Andersons’ party. After Sara climbs out an open window and slides down the building, Chris spots her and they run upstairs to help.
After the group pulls Sara from outside the window, Bleak confronts them. Joe knocks his boss out, before giving him a Playboy Magazine that Daryl had stolen, which contained important notes that the criminals wanted, then says he is getting out of crime. The kids retrieve Brenda from the bus station and rush home, narrowly avoiding the Andersons on the way. Once home, Chris cleans up the mess left earlier, settling into place just as the Andersons enter. As Chris says goodnight to the kids, Brad tells her he understands about her not feeling the same way he did about her and tells her that if they see each other at school the next day, it’s okay if she ignores him. But Chris smiles and tells him she doesn’t ignore her friends. Just as Chris is leaving, Dan arrives with one of Sara’s missing skates. He says he needs a babysitter and is disappointed when Chris says she is retired; he confesses the babysitter was for him. Chris decides that retirement can wait and gladly agrees to babysit Dan. With Sara’s encouragement, Chris and Dan kiss outside as Brad closes the blinds.
In a post credits scene, Graydon is shown standing on the ledge, still trying to find his way to safety.
Adventures in Babysitting (also known as A Night on the Town in certain countries) is a 1987 American comedy film written by David Simkins, directed by Chris Columbus (in his directorial debut), and starring Elisabeth Shue, Maia Brewton, Keith Coogan, Anthony Rapp, Penelope Ann Miller, Bradley Whitford, and brief cameos by blues singer/guitarist Albert Collins and singer-songwriter Southside Johnny Lyon.