The reserved 16-year-old Sophie Birenbaum embarks on an unexpected journey after landing a leading role in her high school's production of Waitress. Just as she is beginning to relish the excitement of this opportunity, she stumbles upon the distressing news that her mother, Elizabeth (played by Stephanie Beatriz), is battling a return of cancer. Although her best friend Carolyn (portrayed by Scarlett Estevez) vows to support her during this challenging time, Sophie's experience becomes complicated when Carolyn's behavior shifts, causing Sophie to feel increasingly isolated.
Seeking to help her daughter find a convincing southern accent, Elizabeth takes Sophie to the mall for some practice with the shopkeepers. By the end of the outing, Elizabeth reassures Sophie that the director made an excellent choice in casting her. However, the situation escalates when Sophie’s father, Ted (played by Max Greenfield), and Elizabeth learn that the cancer is progressing much more rapidly than expected. Elizabeth decides she cannot share this news with Sophie just yet, fearful that it might cause her to abandon the musical.
As rehearsals continue, Sophie learns that her character will share a kiss with her crush, Jack (played by Jack Champion). Just as she is about to confide in Carolyn, another student, Erin (portrayed by Emma McNulty), interrupts with stories from a recent hike. This interaction inadvertently reveals that Carolyn has not only exited the play but has also started spending her time with someone else, leaving Sophie feeling hurt and further distanced.
When Sophie’s grandparents arrive to help the family, tensions rise when her grandmother, Linda (played by Bebe Neuwirth), causes a stir over Sophie’s dress rehearsal coinciding with Mother’s Day. Elizabeth, due to her frustration at Linda's insensitivity regarding her illness, urges Ted to send them away. Venting to Carolyn afterwards, Sophie finds herself invited to a party hosted by Erin, where she ends up getting drunk and tries to sneak back home unnoticed. Unfortunately, the next morning brings the departure of her grandparents, adding to the family’s heavy atmosphere.
In an attempt to celebrate Mother’s Day, the family heads to a deli, but the situation takes a turn when Elizabeth collapses, leading to a hospital visit. The somber news reveals that Elizabeth will be too weak to attend the play and will miss their usual time at the lake. During rehearsal, Sophie witnesses the crew's typical post-show activities, including hookups amidst the excitement. Just before she can find Jack, he kisses another girl, Mallory (played by Elyse Bell), leaving Sophie feeling betrayed.
Unbeknownst to Sophie, Elizabeth privately arranges for the musical's director to send a video feed of the dress rehearsal to their home. When Sophie discovers this revelation, she is overwhelmed and breaks down on stage, unable to continue her performance. She rushes home, confronting Elizabeth about withholding crucial information regarding her health. Elizabeth confirms the grim reality of her situation, leaving Sophie to maintain a brave front for her younger brothers while Ted manages the family deli.
In a poignant moment, Sophie helps prepare her brothers for school and both she and Ted acknowledge that they are not okay. When they arrive at school, Carolyn pledges her support to Sophie, who with open arms accepts the news of Carolyn and Erin being a couple. Initially, Sophie contemplates asking Mallory to step into her role for the performance, motivated by her desire to be with her mother. However, with encouragement, she reclaims her part confidently.
As summer unfolds, the family collaborates with the musical crew to transform their backyard into a beach house setting, where Sophie performs a heartfelt song for her mother, culminating in a poignant tribute that resonates with the spirit of their shared journey.
