Mackenzie "Mack" Martin Elizabeth Lail has spent most of her life preferring the company of adults to that of her peers. Raised by her grandmother, she learns to blend in, but she still feels more at home when conversations lean toward grown‑up topics and responsibilities. At thirty, Mack’s social awkwardness nudges her toward a Palm Springs bachelorette trip for her best friend Carla. She arranges for her neighbor Jack Dustin Milligan to look after her dog Cheese Martin Short while she’s away, yet the two struggle to connect on a meaningful level.
On the first day of the trip, Mack encounters a strange pop‑up tent offering the chance to >become her true self<. The proprietor Luca Simon Rex convinces her to lie inside what looks like an old tanning bed and speaks about who she wants to be. In a moment fueled by a longing to shed the burdens of youth, Mack ages into a seventy‑year‑old woman, and she panics when she catches the drastic transformation reflected in a mirror. Returning to the house, Carla doesn’t recognize her and tries to dismiss her from the trip.
Mack calms Carla by revealing secrets only they share and confirming the story behind her jewelry. Retracing their earlier steps, Carla suggests she should find the tent and Luca. Equipped with a convertible, Mack leaves the group, promising to be at the bridal shower. Back in her apartment, she bumps into Jack and assumes the identity of her aunt Rita Diane Keaton. Rita ends up at Carla’s shower, where she is introduced to Carla’s mother Sharon Loretta Devine and her wine club. Carla nudges her to stay positive and to throw herself into various activities that might coax her body back, but the changes don’t take.
Mack’s agent calls about an upcoming Pilates event she needs to promote, and Rita attempts the routine, though by the end she’s done many exercises in unusual ways. Later, Jack persuades her to join a building‑wide rooftop activity. After the wine club gathering, Rita finds herself part of a social whirl in her building, and she and Jack grow closer on an ordinary lunch outing, where a younger woman questions whether he’s the one with a motherly status. The evolving relationship feeds Mack’s unlikely transformation into a public‑facing persona, and she becomes a surprising social media sensation that echoes across her life.
As Carla’s rehearsal dinner approaches, an Instagram‑driven push keeps Mack juggling two identities, but she ends up missing the rehearsal and catching Carla’s sharp rebuke. Sharon overhears the tension and, along with the wine club, pressures Mack to live fully in the present and not miss out on the best years of life. Spurred, Mack hunts down Luca’s tent, aided by a flyer Carla found, and returns to the site. Inside the broken tanning bed, a very surprised Luca watches as Mack emerges from the device in a euphoric state.
A year passes, and Mack has not only started a relationship with Jack but has also completed a second book. At the book reading, everyone she interacted with as Rita is present, confirming that the journey to discover and reckon with her “true self” has left a lasting mark on both her art and her heart.
