After her erratic mother, Mommers, and patient stepfather divorce, Addison moves into an old, tiny trailer on the outskirts of Schenectady, New York, with her mother. The court has ruled that her stepfather, Dwight, will continue to pay alimony and have given him custody of Addie’s half-sisters, Brynna and Katie. Mommers dislikes the camper and their apparent poverty, but knowing Dwight can only help them so much, Addie stays positive about the situation.
The trailer sits beneath an overpass and trembles with each passing train. Nearby are the laundromat, the fire department and a gas station with a minimart. At the minimart, Addie meets Elliot, the thin, cheerful store owner, and Soula, a large, laughter-prone woman who often seems to need to rest in a lawn chair brought into the store especially for her. Soula lives in a portion of the store dubbed the Greenhouse, at is mostly encased in windows. Elliot and Soula take a shine to Addie and welcome her into the neighborhood.
On one of Dwight’s visits with the girls, Dwight explains that he’s been highered to work on a large renovation project in the next town, and due to its schedule, his visits will be less frequent. Addie is upset, but knows she can’t do anything to change things. She is hopeful for April, when Dwight’s renovation should be over.
At her new school, Addie auditions for the school orchestra. Addie is a flute player and loves music. Due to a learning disability, she struggles to read music but has a good ear. She is anxious during tryouts — her flute was issued to her by her previous school and as she wasn’t given the chance to return it before moving, she feels it is stolen property — but Ms. Rivera is encouraging.
One of the students teases Addie’s new friend Helena, who is heavier and maturing faster than most girls in the sixth grade. Addie sticks up for Helena, and the two discuss puberty on their walk from school. With Soula, Addie discusses health and what it means to be a hero. Addie returns home and makes dinner, as Mommers is too absorbed in the television to prepare food. This is a common occurrence.
Dwight and the girls visit and gift Addie a hamster. Addie names the hamster Piccolo, after the instrument she hopes one day to play well. The family has a wonderful dinner at a local pub. The next day, the pub owner arrives at the minimart while Addie and Soula are chatting. He introduces himself as Rick and leaves a message for Elliot, who is his boyfriend.
A few days later, Addie brings Piccolo to the minimart to show Soula. Finding the store empty, she goes into the Greenhouse and finds Elliot tending to a vomiting Soula. Soula explains that she is battling breast cancer and is reacting to chemotherapy treatment.
Addie heads home that evening as Mommers is about to head out the door. Mommers says she has a job interview. Addie has her suspicions about a job that would interview so late at night. Addie attempts to do some homework while nervously awaiting her mother’s return. Before Dwight had full custody of her younger sisters, Addie remembers when Mommers left the three girls alone in the house for three days.
When Mommers returns late that night, Addie learns she is pursuing a risky business venture and has given her new boss, Pete, Dwight’s most recent alimony check. In the following weeks, new clothes and office supplies appear in the trailer, but not many groceries. When Addie learns that she’s been accepted into the school orchestra and will perform at the Christmas concert, Mommers takes Addie out to dinner using the new credit card from Pete.
On Halloween, Mommers tells Addie she is too old to go trick-or-treating. Then she leaves on an overnight trip with Pete. Elliot and Soula keep her company for the evening and dress her up with Soula’s clothes and makeup.
The next day, Dwight calls to let Addie know he and the girls have moved to a different house and have a new number. He also lets her know about Hannah, whom he’s excited for Addie to meet. Unfortunately, their meeting will have to wait until Thanksgiving at her grandfather’s house, if Mommers consents to the visit.
Mommers does not return until Monday morning and does so driving a new car. She does not explain where she’s been. After school that day, Soula asks Addie whether she is happy at home. Addie doesn’t tell Soula that Mommers had been away all weekend, afraid that if anyone knew, her family would become even more split up than it already is. Addie blames herself for the way things currently are, since she had told Dwight that Mommers had left them alone for those three days and since then is no longer allowed to live with her younger sisters.
Mommers agrees to let Addie visit Dwight for Thanksgiving and the weekend following. At Thanksgiving dinner, Addie meets Hannah, Dwight’s new girlfriend. Hannah owns the inn that Dwight is renovating and plans to open it as a bed-and-breakfast. Hannah, Dwight and the girls live in the renovation together. Dwight and Hannah plan on marrying the following year. Addie is initially wary of Hannah but quickly sees why Dwight and the girls love her.
Over the weekend, Addie watches this half of her family carry on their normal routines of work and play around the inn in-progress. Addie overhears Dwight and Hannah discussing the (unlikely) possibility of adopting Addie into their family. Addie invites all of them to her Christmas concert.
Addie returns to the trailer and to Mommers after the long weekend. On Monday morning, Addie gets her first period. Because her friend Helena has already experienced her period, Addie is calm about the situation and asks Mommers for some pads to take to school. At school that day, Ms. Rivera gives Addie a solo part in the Christmas concert.
Mommers gives Addie an immodest dress to wear at her concert. Addie is uncomfortable in it, but Mommers insists that Addie is a woman now and can show a little skin. When Dwight stops by with his check and sees the dress, he tries to convince Mommers to find an alternative outfit, but Mommers insists and Dwight has little say in the matter.
On the day of the concert, the orchestra rehearsal goes incredibly well. Addie is excited, but also nervous about the dress she must wear. Helena tries to encourage her, and Addie promises she won’t skip the concert. That night, however, Mommers doesn’t return home to pick up Addie and drive her to the concert as planned. Eventually Dwight picks her up and rushes her to the concert. As she’s approaching the stage, Addie sees the music teacher from her old school in the front row. Already flustered at being late and convinced her teacher will be angry at Addie for playing the flute she stole from her former school, Addie refuses to play in the concert.
Afraid that her classmates will never be able to count on her after the concert fiasco and still feeling guilty over the stolen flute, Addie resolves to give up music entirely. She walks more than a mile through the snow to her old school, where she leaves her flute. Her grandfather, Grandio, spots her on her walk home and takes her out to lunch before bringing her back to the trailer.
At school she explains to Ms. Rivera why she backed out of the concert at the last minute and will not accept the offer of a replacement flute. Soula and Elliot give Addie a pair of boots for Christmas, having seen Addie wear sneakers in the snow. Soula also gives Addie a new pack of underwear, having heard that she’d started her period.
Mommers agrees to let Dwight take Addie for half of Christmas break. On Christmas day, after a rushed gift exchange, Mommers tells Addie that she is pregnant with Pete’s baby. Addie is upset at the idea of another little life thrown into the mix of her confusing family. Rather than attempt any justification, Mommers leaves to spend the rest of Christmas with Pete — who doesn’t know that Addie exists.
Addie catches the bus the next day to see Dwight and her sisters. Cleaning the kitchen after dinner, Dwight and Addie have a heartfelt conversation about Mommers, Brynna and how all three girls are coping after the divorce. The rest of Christmas break, Addie is grateful to be included in her family’s antics, yet hesitant, knowing she’ll have to leave again.
In the following weeks, Mommers returns to the trailer less frequently and for shorter amounts of time. Due to the snow, Dwight’s truck isn’t running and so he cannot visit for the time being. Addie doesn’t tell Dwight that she’s alone more often than not.
After a several-day absence, Mommers returns home to cash Dwight’s check. She buys Addie minimal groceries and keeps the rest to give to Pete for their business. Grandio stops by to check on Addie on a day when Mommers is out. Seeing some food in the cupboard, he leaves satisfied that nothing is wrong.
In mid-February, Dwight arrives at Addie’s school to check up on her, as neither she nor Mommers has answered his calls lately. Dwight has purchased a roll of lunch tickets for Addie to use at school, and also gives her a bank card to make withdrawals from his account if she ever needs cash. Dwight asks Addie to keep the card a secret from Mommers. He also asks when she would come visit again.
Addie confesses that she’s struggling to live between her two families and having an especially hard time adjusting to Mommers’ normal after spending time with Dwight’s. Addie does not want to see Dwight or her sisters, at least for a while. The decision upsets Dwight, but he understands.
Addie spends more time with Soula and Elliot at the minimart. Soula has grown weaker and doesn’t eat much, but she’ll eat Addie’s toast dinners. Addie comes home from dinner with Soula to find Mommers making an enormous amount of tacos. Addie accuses Mommers of preparing for another long absence, which Mommers doesn’t deny. Addie cleans most of the kitchen, but Mommers promises to clean the last of the dishes.
Mommers leaves without cleaning the dishes as she’d said. Addie sees the dirty pan of grease on the stove and decides she won’t clean up after Mommers anymore. She leaves the pan on the burner.
Four days later, Addie turns on a burner to make hot cocoa before school. When she gets out of the shower, she finds the dirty pan on fire. She had turned on the wrong burner. The fire extinguisher doesn’t work, and the fire is spreading, so Addie scrambles to get Piccolo and herself out of the trailer.
Soula ushers Addie away from the burning trailer and toward the minimart, but is too weak to make the full distance back. Addie runs ahead to get her lawn chair. The fire department eventually comes, but the trailer is now unlivable. Amid the excitement, Soula calls a social worker, who arranges for Addie to live with Grandio. Addie leaves Piccolo with Soula temporarily, and calls Soula her hero.
Dwight and the family visit Addie that evening at Grandio’s house. Dwight makes it clear that he cares more about Addie’s safety than his incinerated trailer. Over the next few days, Addie adjusts to living at Grandio’s. The social worker tracks Mommers down, but Mommers is not permitted to visit Addie.
Addie goes to pick up Piccolo. When she arrives, she learns that Soula has passed away. Elliot gives her an envelope containing a goodbye letter and $300 to help buy her own flute.
Mommers arrives uninvited to see Addie and try to explain things. Grandio tries to make her leave, but Addie wants to say goodbye. Mommers is trying to make a new family with Pete, who will help her with the new baby. Addie describes her hope of a more normal, stable family and confesses that she feels Mommers can never quite get there. When Mommers leaves, Grandio goes on one of his tirades about what an awful woman she is. Addie shouts at Grandio, who realizes that complaining about Mommers won’t change anything about their situation.
After a few more conversations with the social worker and a signature from Mommers, Dwight officially adopts Addie. She finishes out the school year with Grandio before moving to the inn with Dwight, Hannah and her half-sisters.