Alice, portrayed by Dakota Johnson, decides to take a break from her college boyfriend Josh (Nicholas Braun) and relocates to New York City to work as a paralegal. She moves in with her sister Meg, played by Leslie Mann, who is an OB/GYN adamant about not wanting children or any romantic entanglements. In her new environment, Alice connects with her adventurous co-worker Robin, brilliantly brought to life by Rebel Wilson, who enjoys a lifestyle filled with parties and casual encounters. Alice also forms a friendship with local bartender Tom (Anders Holm), a man fully committed to his bachelor life, who casually dates women, including Alice herself.
During her time in the city, Alice confides in Tom about her struggle with identity, revealing that she has spent most of her life in relationships. In response, Tom offers her practical advice on how to embrace the single life, suggesting she rid herself of anything that resembles a romantic connection. Alice tries to reconnect with Josh, but her plans are thwarted when he reveals he's dating someone new, leaving her heartbroken.
In the meantime, Meg's perspective shifts when she decides to pursue motherhood through a sperm donor. She soon finds herself in a relationship with younger Ken (Jake Lacy), shortly after confirming her pregnancy from In Vitro fertilization, yet she keeps this news hidden from him. Their relationship takes a turn when Meg asks Alice to move out, primarily due to the chaotic influence of Robin.
As the story unfolds, we see Lucy, played by Alison Brie, struggling in her dating life, which catches Tom's attention and stirs feelings inside him. As Meg embarks on her own romantic journey, Alice yearns for Josh, prompting her to seek out new connections at an alumni event where she meets David (Damon Wayans Jr). This encounter sparks a new relationship for Alice, who hopes to move on.
However, Lucy experiences heartbreak when her brief relationship crumbles. Feeling lost, she soon finds solace in George (Jason Mantzoukas) at her volunteer job. Amidst the holiday festivities, Alice and Robin attend a party hosted by Josh, which reignites Alice's emotions when she sees him with his new girlfriend. It’s during a moment of solitude that she meets David again, leading to an exciting yet complicated relationship.
As challenges arise, including a confrontation during Alice's birthday party where multiple exes show up, Alice navigates through her feelings and life changes. In a moment of impactful realization, Alice learns Josh’s true intentions for their encounter, ultimately deciding to embrace her independence.
The climax reaches a pivotal moment when Meg, going into labor, needs immediate help from Alice, leading to a heartwarming reunion and resolution. In the film's final segments, we see Alice find closure and perspective on her life choices while cherishing the memories of her single days. The narrative closes with Alice hiking alone in the Grand Canyon, fulfilling her lifelong dream of witnessing a New Year’s sunrise, symbolizing newfound independence and self-discovery.
