INT. SHERRIF'S OFFICE - DAY - HEIDI is sitting in the Sheriff's office with a jar of jelly beans and a desire to escape out the window as another DEPUTY stands guard. COUNTY SHERRIF ROY FRANKLIN enters and proceeds to grab a coin, which he asks Heidi to call. She hesitates but eventually acquiesces and gets it right. He does this a total of ten times and she gets them all right. The Deputy is spooked but Heidi knows that it means BERNIE called, a fact Roy confirms after commenting that she's going home with him instead of being booked as a runaway. Heidi remarks she's not a psychic and that she didn't run away.Heidi is next seen at a BUS TERMINAL in RENO, NEVADA and eventually asks a PUNKED-OUT GIRL to buy her a ticket since she is underaged. The Punked-Out Girl concedes after. small spat and asks where Heidi got all her money from - as it is all silver dollars. Heidi simply replies that she's lucky. We learn Heidi is traveling to LIBERTY, NEW YORK. Heidi sees an opportunity and asks ALICE WILINSKY, an elderly woman with her hands full, if she'd like any help so that she can proceed in her travels inconspicuously. Alice agrees and Heidi boards, though the Bus Driver is suspicious.Heidi winds back the clock a few days where she is in the KITCHEN with Bernie and is doing schoolwork. They are interrupted by MAMA and traverse through Bernie's cluttered 'hoarder' home while discussing future lesson plans, then they transition into a SEPARATE APARTMENT that is open and colorful. Mama is inside - she is Heidi's mother and suffers from a mental disability which severely limits her vocabulary, nevertheless Heidi's relationship with her blossoms.Outside, Heidi is speaking with ZANDER - a neighbor of similar age who appears far more childish. They are speaking about ZANDER'S FATHER and his heroics when Zander crushes an ant. At the same time Bernie is showing Mama how to open cans in the kitchen, and Bernie's love for her becomes very deep and apparent. Outside again, Zander and Heidi overhear an argument from his parents inside that doesn't end pleasantly. Heidi is silent and Zander thinks she's judging him, so he runs off and jabs at her family's lack of normalcy. Later at night Heidi is making one of her LISTS when she asks Bernie why people lie. Bernie explains people lie because the truth is too hard to handle.Back onto the BUS, Heidi and Alice are handling an array of kittens as Alice rambles about her large family and the impressive amount of other Alices in it. Heidi is obviously not very enraptured by the conversation but pays attention either way, and lies when Alice asks when her birthday is - since Heidi isn't sure herself.In the APARTMENT Heidi tries to vacuum but it incapable since it sends her Mama into a frenzy. The VACUUM BREAKS and Bernie tries to fix it but comes up short on money, forcing Heidi to take action. Heidi comments on Bernie's AGORAPHOBIA (fear of leaving one's house) and how it stems from her father dying of a heart attack years ago. Together Heidi, Mama, and Bernie practice going to the bus stop inside their home so they can get the vacuum fixed. Heidi tries to proceed to accomplish the same thing in public but ultimately fails; despite Mama's radiance and excitement, as soon as the bus approaches she has another frenzy and Heidi is forced to return home. Bernie comforts Mama as she repeats a phrase over and over by reliving what Bernie later tells Heidi is a MEMORY. Mama whispers 'SOOF', which sparks more confusion, and Bernie tries to explain the past again but Heidi is not satisfied and wants to know more than Bernie can provide.On the Bus Heidi is making another list aside a sleeping Alice. This list is titled THINGS I'VE NEVER SEEN BEFORE, to which she adds MY FAMILY. Heidi pulls from her pocket a tiny souvenir teaspoon and tries to go to sleep.Mama is having a particularly bad headache as Heidi presses Bernie for more answers about her Mama but still turns up empty-handed. Heidi adds 'soof' to her Mama's list of words, making it twenty-three long. Later Heidi presses her mother on what 'soof' is and becomes progressively more irritable. When Bernie chastises Heidi, she storms off and Bernie follows. Heidi proceeds to tear open the drawers and pull out random objects as she asks Bernie what her real name is, what her mother's real name is, and who pays the rent. All of these questions have the same answer: I don't know. Mama picks up the discarded items and Heidi discovers a roll of film that she sends to be developed and eagerly waits for it to arrive. When it does, Bernie and Heidi find a wealth of pictures that include Heidi's Mama, her grandmother, and some other people in a hospital setting. Heidi has more questions than ever and wants to wake Mama from a nap, but Bernie won't allow it. This sparks an argument as Heidi tries to look for more answers and criticizes Bernie's maternal fear since she's not actually Heidi's mother. When Heidi tries to apologize Mama wakes up and Heidi presses her for information with growing pressure. Bernie demands Heidi stop and she stomps off after tearing the picture in half. That night Bernie tries to comfort Heidi but Heidi resolutely states that she needs answers even if Bernie cannot provide them.At a DIFFERENT BUS STATION Heidi grabs a burger and learns that her hometown is in the midst of a storm. She tries to call home because she knows her Mama is afraid of storms but the call doesn't go through. At home the power goes out as Bernie tries to assuage Mama's fear. Earlier a quick moment flashes that shows Heidi taping the picture she tore back together and asking Bernie what the sign in it says. This leads to Bernie calling HILLTOP HOME but she is either put on hold or promised a call back from THURMAN HILL that never comes. Heidi insists they go to it and persuades Bernie to try to leave the house, but she collapses one step outside the door and Heidi is forced to employ Zander's help in getting her back inside. This leads Heidi to the conclusion that she must go alone, so she packs and gathers everything for the journey. In DOWNTOWN RENO Heidi remarks on her LUCK and employs it to win in her final attempt at a slot machine, which gives her all the money necessary to begin the trip.Once more alongside Alice on the bus, Heidi digs into a pie the older woman made her with vivaciousness. Alice asks Heidi about her family and she lies, saying it's big then commenting about how she's named after a movie with Shirley Temple in it. Alice asks more questions that plunge Heidi into a hole as her lies spiral out of control. Alice eventually exposes Heidi for lying and when returning to her seat, Heidi is now alone since Alice moved multiple seats forward. At home Bernie is comforting Mama when Heidi calls but fails to make a solid connection. In a BAKERY at another stop Heidi purchases a cake and exposes her money to TWO PUNKS who later rob her of all of her coins. On the bus the NEW DRIVER questions Heidi who is struggling to spin a convincing tale, but the previous bus driver who was suspicious of her confirms her story and she is allowed on. When she arrives in Liberty, Heidi calls Bernie and expresses her feelings of fear and being lost. Bernie tries to convince Heidi to come home but she hangs up and eventually catches a ride in a Cab by guessing how many jellybeans were in the jar on his dash.Heidi arrives at Hilltop Home Heidi and overhears ELLIOT say Soof when he sees her. RUBY, Elliot's caretaker, expresses momentary delight that Heidi might be the long-sought after Soof but their hopes are crushed when he gets closer and confirms it's not her. Thurman Hill enters and when Heidi explains who she is he demands Elliot and Ruby leave with an unfamiliar coldness. He is furious at Heidi and accuses her of wanting more money as well as slandering her with other confusing remarks. Elliot has a tantrum that tears Mr. Hill away and Heidi sees an officer in the doorway, which throws her into a sprint.The story resumes to the first scene with Sherriff Roy. They discuss Heidi's peculiar luck and then Roy brings Heidi back to his house for dinner. His wife is Ruby from Hilltop Home, and she realizes that the man in Heidi's pictures with her mom is Elliot and Mr. Hill. Heidi calls Bernie and tries to calm her panicking Mama but is mostly unsuccessful. The next day Heidi wakes up to find Roy has gone up to Hilltop Home without her. In her rush to join them Heidi searches through the drawers only to find unused baby clothes, to which Ruby explains that she'd had multiple miscarriages. Heidi apologizes and has breakfast with Ruby when Roy returns to bring Heidi back to Hilltop. As Heidi is leaving Bernie tries to suddenly convince her to come home over phone because of Mama, but Heidi is persistent and goes to Hilltop anyways. There she finds Mr. Hill with his lawyer, DIETZ, who starts explaining things but only confuses Heidi further and increases her impatience. When she demands answers, Mr. Hill asks everyone else to leave and says he knows everything about her.Eyes gleaming with terror, Bernie is one the phone with an EMERGENCY CONTACT and is trying to calm down Mama. Bernie waits for the EMTs but Mama only whispers 'soof' then closes her eyes.Mr. Hill explains the pictures with names, revealing her mother's true name is SOPHIA DEMUTH and that he only accepted her into his home as a charity case per request of Sophia's mother. Elliot, Mr. Hill's son, became her best friend and eventually fathered Heidi, though upon news of Sophia's pregnancy, Sophia's mom demanded Mr. Hill give them money - therefore facilitating the endless flow that had allowed Heidi and Mama to live in Reno. He was not to contact them and agreed to the conditions. Heidi also learns her grandmother is dead.Desperate, Bernie tries to flag down the EMTs but they are going in the opposite direction. As they continue to get farther away Bernie is forced to face her fear and leaves the apartment, going far enough to get the EMTs and urge them upstairs to get Mama. Bernie crumbles to the ground in a heap. Back at Hilltop, Heidi learns her grandmother was hit by a bus shortly after Heidi's alleged birthday in February. In Reno Bernie gets back to her feet and returns to the apartment. Mama looks peaceful and whole as the EMTs draw a sheet over her face.Outside on a swing Heidi is pushed by her father, Elliot, as she remarks upon her discovering her family and her mother's name. Mama couldn't pronounce Sophia so she always said So B. It, and Elliot always said Soof. Later, Heidi tries to share all of this exciting information with Bernie, who is unreceptive. Ruby tells Heidi what has happened and Heidi breaks down. She starts a new list, titled - THINGS I'LL MISS ABOUT MAMA - with one lone entry: EVERYTHING. She tears everything out of the notebook and shreds each page by hand. Roy tries to comfort her by offering a distraction and speaking with her, and Ruby offers to give Heidi a haircut. Heidi threatens to hurt herself as Ruby comforts her. At the burial of her mother, Heidi reflects on the names of her Mama and shares that Soof wasn't her name, it was what she called love. Mr. Hill offers Heidi pictures and files on her Mama, as well as the opportunity to be integrated into the family. Later, as she makes another list, Ruby and Roy confront Heidi about an opportunity for her to join their family. She calls Bernie but is unable to come to a sure conclusion, since she's just discovered a whole new side of family in Liberty. Heidi remarks that the trip was about family as she returns home to Bernie in Reno.Back home, happiness and change find Heidi in far higher spirits. She gets off the bus from school with Zander and returns home to a new Bernie: one who can actually leave the house. Heidi shares she left her luck in Liberty for Roy and Ruby, who now have a baby. Supper is served in a small two-person family with endless love between them, and Mama watching from above.