Somebody I Used to Know - It’s like you build your whole life around this one thing, and then what if it was the wrong thing?

The movie follows a TV producer, Ally, who tries to get her life back on track after a career downfall. As a showrunner of a dating reality show, she has been so focused on her show that she has neglected her personal life. Knowing that her show will end after this season, she feels lost and decides to take a break to visit her mom, because she hasn't been returned to her hometown for so long. At a local bar, she runs into her ex-boyfriend, Sean. She has nothing else to do so she spends her whole day hanging out with Sean, reminding her why she fell in love with him in the first place. At the end of the day, Sean rejects her invitation to stay overnight, so she visits Sean's house the next day. Ally learns that Sean has engaged with Cassidy and they are getting married this weekend. Ally learns from Sean's friend that he didn't run into her by accident. Sean knew she was there before going to the bar. Ally realizes they still have feelings for each other but also unresolved issues from their past, so Ally accepts Sean's mom's invitation to be the photographer of the wedding to capture the happiest moments, hoping to win Sean back. Ally discovers that Cassidy is in a band, and Sean insists that she has to quit her band after they get married. She unwillingly agreed, so her band performs the very last time before the wedding. Ally shared that she left Sean to pursue her career in Hollywood many years ago, and she never regretted for her decision. She also learns that Cassidy doesn't have a good relationship with her family and didn't invite them to the wedding, so she plans to sabotage the whole thing by inviting them. When Ally and Cassidy have spent more time together, Ally figures that Cassidy is similar to her younger self, and they both love the same guy. Ally begins to bond with Cassidy and end up streaking together. Cassidy also reveals that one of the reasons they were getting married in the first place is that she thought she was pregnant. Ever since then, Sean has wanted her to quit the band and be a stay-at-home mom. Ally sympathize Cassidy because she had gone through similar things with Sean too.

Cassidy's parent come to the wedding unannounced, which triggers Cassidy. Cassidy thought Sean invited her, and Sean is mad that she lied to him that her parents didn't want to come. They have an argument, and Ally doesn't want them to break up because of a mistake she made, so she tries to bring them together. Sean apologizes to Cassidy for trying to control her life and promise he will let her do whatever she wants. Meanwhile, Ally's reality show got picked up but she will let her assistant to be the new showrunner. She leaves her hometown and takes up hosting a new documentary about nudists.

Ally has always thought that she made the right decision when she decided to leave her family behind and pursue her career in Hollywood. Her own show has become her only achievement ever since then. When she learns that her show got cancelled and was forced to take a break, that's the time when she realizes that she isn't happy as before and she is nothing without her now-cancelled show. It is never too late to plan a new chapter of life.