As Chris Parker, a 17-year-old girl, faces a disappointing anniversary, she decides to invite her friend Brenda over to uplift her spirits. However, after some persuasion from her mother, she reluctantly takes on the responsibility of babysitting the spirited eight-year-old Sara Anderson and her 15-year-old brother Brad. Initially hesitant, Chris changes her mind upon receiving a panicked call from Brenda, who has found herself at a downtown bus station. Determined to make the best of the situation, Chris brings the kids along for the adventure.
Their journey quickly takes an unexpected turn when they suffer a flat tire, leading them to encounter Handsome John Pruitt, a laid-back tow truck driver who offers to cover the repair costs—only after Chris realizes she left her purse at the Anderson household. As they make their way down the bustling freeway, Pruitt receives a shocking call from his boss Dawson, revealing that his wife is having an affair. This revelation infuriates Pruitt, prompting him to leave abruptly to confront the situation, all while unintentionally causing damage to Chris's mother's car in the chaos.
In a whirlwind of events, the group finds temporary refuge in the Cadillac of Pruitt's wife's lover, but their luck runs out when it's stolen by Joe Gipp, a crafty thief. Following a series of misadventures, they end up on the South Side of town where they stumble into a multi-state ring dealing with stolen cars. Here, they encounter Graydon, the operation's second-in-command, who scolds Joe for his reckless behavior. Nevertheless, Chris's quick thinking allows them to break free from their captors and make their way to a local blues club. There, in an unforgettable moment, they perform an impromptu blues number alongside Albert Collins, capturing the audience's hearts and earning a standing ovation.
Just when they think they're in the clear, Joe, Graydon, and their boss Bleak catch up to them at the club. However, the club owners provide a much-needed distraction, shielding their patrons from the unwelcome visitors. Amidst the unfolding drama, Brad hesitantly confides in Chris about his feelings for her, only to be met with disappointment as she subtly reminds him of his youth and their circumstances.
As things take a chaotic turn, Chris finds herself resonating with Brenda's struggles when she and Daryl Coopersmith step in to help a runaway streetwalker. This act of kindness escalates into pandemonium as Graydon and Bleak relentlessly pursue them once more. Their escape leads them onto the Chicago "L" train, where they unwittingly get caught up in a violent gang fight, resulting in Brad sustaining an injury. Seeking refuge, they rush to the university hospital, where Brad receives emergency care.
In the aftermath of all these events, the group crosses paths with Pruitt again, who is now in hiding from his previous troubles, while Dawson appears more interested in payment than help. However, fortune smiles upon the kids when they stumble into a lively fraternity party, where Chris catches the eye of Dan Lynch. He gestures a living soul to their plight and generously donates $45 to assist their cause.
As they attempt to return to Dawson's garage for their car, they encounter another hiccup—Dawson himself. In a lighthearted moment, little Sara mistakes him for Thor, causing a humorous interaction that ends with Dawson eventually relenting and agreeing to lend the kids their vehicle, spurred on by Sara's special request.
Tensions rise anew when Joe Gipp updates Bleak on their ordeal. Meanwhile, Chris confronts another round of emotional turmoil when she realizes Mike has ditched her for another girl at the restaurant where they planned to meet. Frustrated, Sara wanders off to explore a nearby toy store while Chris angrily vents her feelings to Mike. Brad tries to defend Chris but struggles until Daryl steps in, leading to an explosive confrontation that sends dinner crashing down.
As chaos erupts, Sara mysteriously vanishes but promptly reappears on the rooftop of an office building after an audacious slide. Chris spots her and, with the group, rushes to the rescue, inadvertently breaking into the middle of a chaotic Anderson family gathering filled with laughter, tears, and surprising moments. As they work together to save Sara, the atmosphere thickens with tension as Bleak confronts the kids. In a pivotal moment, Joe takes down Bleak with a swift strike, and amidst the fray, Daryl's pilfered Playboy magazine proves crucial for the criminals.
Ultimately, the gang manages to safely retrieve Brenda from the bus station just before an awkward encounter with the Andersons on the highway. Back home, Chris busies herself with cleaning up the aftermath of the chaotic adventure, finding a sense of peace as the Anderson family approaches her door. After wishing the kids goodnight, Brad attempts to comfort her with the notion that it's okay to ignore him at school, but Chris warmly reassures him that friendship transcends any barriers.
In an unexpected twist, Dan bursts in, holding one of Sara's missing skates. With a humorous reveal about needing a babysitter for himself, Chris, always one to lend a hand, decides her break can wait and agrees to keep an eye on Dan, much to Sara’s delight. The evening wraps up with a tender kiss between Chris and Dan, as Brad discreetly closes the curtains on the heartwarming scene.
In a whimsical post-credits scene, we see Graydon precariously positioned near the edge, still searching for his footing amidst the chaos that has ensued.
