As the story progresses, Shirley Lyner's (Waterston) calming voice introduces a unique babysitting service where middle-aged men and teenage girls gather in a cozy cabin setting. A flashback reveals a pivotal evening when Shirley is picked up by Michael Beltran (Leguizamo) for a babysitting job. Throughout the evening, they indulge in a flirtatious dinner, their chemistry evident as they share their marital frustrations. Michael's discontent with his wife Gail (Nixon), alongside Shirley's perception of her peers as immature, creates a complex web of desires and obligations.
As the plot unfolds, Michael's friend Jerry (Comeau) presents him with a business proposition, sparking tension within his marriage due to Michael's interest. In the midst of this, Michael's curiosity is ignited by a deserted train yard behind their restaurant, an area that Gail dismisses. It is in this intriguing backdrop that Michael and Shirley share a romantic kiss during a late-night adventure, leading them to realize they cannot continue this forbidden path. Regardless, Michael compensates Shirley with extra payments for her babysitting services.
Word of the babysitting arrangement spreads, reaching Jerry. Michael confides in him, while Shirley's friend Melissa (Lauren Birkell) uncovers the truth. Curious, Michael inquires if any of Shirley's friends could also "babysit," prompting Melissa to offer her help. They then convince their friend Brenda (Louisa Krause) to join the venture, leading to the successful launch of their babysitting business, complete with professionally designed business cards.
Trouble brews when Brenda invites her aggressive stepsister Nadine (Halley Wegryn Gross) to join their operation without Shirley's approval. Unbeknownst to them, Nadine starts her own rival babysitting service, siphoning off customers from Shirley's business. Tension arises when Shirley confronts Brenda, who agrees to help find evidence against Nadine. When they find nothing incriminating, Shirley and Melissa are determined to dig deeper.
With Michael now on high alert, they investigate Nadine's locker but come up empty-handed. To distract from their true intentions, the trio resorts to vandalizing the school, resulting in a mandatory assembly the following day. During this meeting, Shirley asserts her authority, calling the girls to the band room to address the conflict. She demands that Nadine stop her secretive operations, proposing to share 20% of profits in exchange for cooperation. Once peace is restored, the girls are sent home.
In a clever twist, Melissa provides Shirley with forged permission slips for a weekend trip to Jerry's secluded cabin, while the men disguise it as a "business retreat." However, as Michael becomes increasingly wary of Shirley's closeness to other men, Jerry secretly begins to supply drugs at the gathering and attempts to take advantage of Brenda.
Following these events, Brenda declares she wants out, and Shirley supports her decision. Fearful that Brenda might expose their activities, Melissa orchestrates intimidating confrontations with Brenda's brother, a move that doesn't go unnoticed. Eventually, during a lunch meeting, Shirley discovers Melissa's plot and expresses her frustration.
As personal tensions rise, Michael's wife confronts him about his emotional detachment and the web of lies he's spun about his job. For the first time, Michael voices his frustrations, only to receive candid responses from Gail. In a moment of desperation, he implores Shirley to leave everything behind with him. However, she stands firm, reminding him that their relationship is strictly professional. As her demands escalate, she walks away, leaving Michael in despair.
Meanwhile, Melissa becomes obsessed with finding Brenda but finds herself continually frustrated in her search. Her efforts finally lead her to Nadine, who is babysitting unsuspectingly. Enlisting Jerry's help, Melissa tracks down the young girl just in time for Jerry to come to Nadine's rescue, confronting a threatening figure in the process.
In a heartbreaking moment of realization, Shirley reflects on the troubling truth about her own father’s past relationship with Nadine, sending her spiraling into despair. As the chaos resolves, she observes Michael with his family and catches his glance before he walks away, symbolizing the end of their affair.
In the final voiceover, Shirley introspects on the impact of this tumultuous chapter in her otherwise mundane life, hinting at deeper themes of longing and regret.
