Plot
18-year-old Morgan Davidson discovers that she is pregnant by her boyfriend, Chris Grant. She confides this to Jonah Sullivan, her sister Jenny's boyfriend and Chris's best friend, who secretly has feelings for Morgan.
Seventeen years later, Chris and Morgan are married and raising their teenage daughter, Clara. Jenny and Jonah have recently reunited after years apart, and have a son, Elijah. One day, Clara encounters her classmate Miller Adams moving the city limits sign. She helps him, then drives him home. They learn that they both have aspirations of working in film.
While talking to Jenny about Miller via text, Clara mentions that Miller has a girlfriend called Shelby. Jenny cautions her not to meddle in their relationship and to not be the "other girl." Morgan and Jonah speak privately about his feelings for her, but she insists it is too late for them, as her daughter comes first. Clara later learns that Shelby broke up with Miller over the budding attraction between the two.
After discovering Chris and Jenny have died in a traffic accident, Jonah and Morgan conclude that they were having an affair. Morgan organizes a funeral for Chris. During the service, Clara leaves to smoke marijuana with Miller. Morgan finds them and grounds her. In the ensuing argument, Clara asks her mother why she did not organize Chris and Jenny's funerals together.
Later, Jonah and Morgan locate Chris's car in a hotel parking lot, confirming the affair. Morgan beats the car before driving it home. Clara questions Morgan about the damage, but she declines to explain. The teen later sneaks out to see Miller, returning to find that Morgan has destroyed the kitchen door.
Jonah hands Elijah over to Morgan the next day, suspecting Chris may be Elijah's biological father. Clara later confronts Jonah about this and persuades him to continue his parenting responsibilities, with she and Morgan agreeing to help however they can.
The next day, after moving the city limits sign again, Miller confesses to Clara he fears if he leaves for college, nobody will look after his grandfather. At the end of the night, Clara and Miller kiss. They later convince Clara's best friend Lexie to ask out Miller's friend Efren. At home, Jonah plays Morgan a song that reminds her of a moment they shared as teenagers.
Morgan expresses disapproval with Clara and Miller's relationship, knowing that they began flirting while he was dating someone else. Morgan and Jonah later find hidden letters from Jenny to Chris, which he wants to ignore, while she does not. Morgan points out a painting that Jenny suggested she buy Chris for his birthday although she hated it, so they both egg it. Overtime, Morgan distracts herself with remodeling, while Clara prepares college applications, and Jonah continues to take care of Elijah
After walking in on Jonah and Morgan kissing, a mortified Clara tells Miller she wants to lose her virginity to him that night. They start to become intimate until she begins crying, realizing that her actions are motivated purely by spite toward her mother. He stays overnight to keep her company. In the morning, Morgan finds them asleep together. He leaves, while Clara gets grounded.
Later that evening, Morgan hosts an awkward birthday dinner party for Clara, inviting Miller, Lexie, and Jonah. Clara and Morgan bicker, resulting in Clara announcing that her dream college has accepted her with a scholarship. Upset with getting tangled in Clara's family drama, Miller leaves. A devastated Clara visits Chris and Jenny's graves with Lexie to share a drink, where Morgan finds them.
The next morning, Morgan tends to Clara's hangover and finally reveals the truth after Clara expresses fear that she inadvertently caused Chris and Jenny's deaths by texting the latter. Morgan clarifies that Chris was the one driving, imploring Clara not to blame herself. Morgan and Clara reconcile and give each other their blessing to be with people they love. Clara later texts Miller an apology, and they reunite at the movie theater. That night, Morgan and Jonah have sex and burn Jenny’s letters.
The family holds a party, where Miller plays a video for Clara, revealing he has been in love with her for two years and was prepared to break up with Shelby the first day they moved the city limits sign. She accepts his invitation to the prom. She and Morgan privately express mutual love and pride for each other. Some time later, Clara and Miller have finish moving the city limits sign to as close to his house as possible, finally giving Miller the chance to order from the pizza place.
