In Los Angeles, 2003, after an evening filled with poker and playful banter, [Debbie Dunn](reese-witherspoon), portrayed by the talented [Reese Witherspoon], and [Peter Coleman](ashton-kutcher), played by [Ashton Kutcher], find themselves sharing a passionate night together at Debbie's home. However, when Peter later contacts Debbie, he reveals that he is not interested in a serious relationship, stating he is too unpredictable for commitment.
Fast forward twenty years, and the pair have evolved into the best of friends. Peter has relocated to New York City, becoming a successful businessman, while Debbie stays in Los Angeles, working diligently as an accountant at her son [Jack's](wesley-kimmel) school. On Peter's birthday, Debbie calls him to discuss her upcoming trip to New York, where she plans to enroll in an accounting program to secure a better-paying job—one that is crucial for covering Jack's medication, which costs $1,000 monthly and will only be insured for another six months. During her visit, she will be staying at Peter's apartment.
Debbie's ex-husband's actress girlfriend, [Scarlet](rachel-bloom), played by [Rachel Bloom], is meant to look after Jack while Debbie is away, but she bails last minute to pursue a role in Vancouver. Understanding Debbie's anxiety about leaving Jack alone for a week, Peter, who recently experienced a breakup and finds himself between jobs, generously offers to travel to Los Angeles to take care of Jack, who is now a teenager. He playfully refers to Debbie's parenting style as "Saran Wrap parenting."
Debbie is depicted as an exceedingly protective mother, dictating Jack's social interactions at school, while Peter grapples with his relationship with his current girlfriend [Becca](vella-lovell), played by [Vella Lovell]. She has yet to meet Debbie and grows increasingly uneasy about Peter's frequent communications with her. After Peter hesitates to reassure her, Becca ends the relationship.
In California, Peter witnesses firsthand the extent of Debbie's overbearing parenting and takes it upon himself to help Jack unwind. He discovers Jack's interest in hockey, despite Debbie's warning about its dangers due to a past injury. Bureaucracies of Debbie's stricter rules emerge, like banning takeout and disallowing Jack from watching TV before or during meals.
As Peter settles in, he gets sky-box tickets to a Los Angeles Kings hockey game, hoping to encourage Jack to invite friends, but not all goes as planned when they neglect him. Meanwhile, in New York, Debbie is attending her accounting classes, where she encounters [Minka](zoe-chao), portrayed by [Zoe Chao], who reveals to Debbie that Peter has authored a novel, something she had never known. Eager to support Peter, Debbie reads through the manuscript and finds a deep appreciation for his work. She pretends to be an editor to convince Theo Martin, a book publisher portrayed by [Jesse Williams], to take a chance on Peter's novel.
As Peter becomes increasingly close to Jack, he finds himself bonding with Debbie's gardener [Zen](steve-zahn), played by [Steve Zahn], discovering Zen's success outside of gardening. Meanwhile, Debbie's relationship with Theo grows, leading to a romantic night together, but complications arise when Peter witnesses this through a hidden camera in his apartment.
On the last day of her New York trip, Debbie passes her exam and stumbles upon Peter's cherished mementos of her, hinting at unexpressed feelings. Theo proposes to keep dating her, but she admits her heart belongs to another. Back in Los Angeles, Jack's hockey tryout goes poorly, resulting in an injury. Despite this, Jack enjoys his time with Peter and encourages his mother not to blame him for the mishap.
In a climactic reunion at LAX, Peter confesses his love for Debbie during a heated exchange, culminating in a passionate kiss. Six months later, Peter achieves his dream of becoming a published author and moves in with Debbie, who has become an editor at an indie publishing house, while Jack proudly plays on his hockey team.
