Milla, a seriously ill teenager falls in love with a drug dealer, Moses, her parents worst nightmare.
Milla Finlay is a terminally ill teenage girl who falls in love with older drug dealer Moses, to the chagrin of her parents Henry and Anna. Although Moses initially spends time with Milla to get to her drugs, he also develops genuine feelings for her and eventually starts to earn trust among her parents, who are dealing with the grief of their daughter’s illness differently (Anna takes antidepressants while Henry almost engages in an affair with their pregnant neighbor).
After Milla’s birthday party, she and Moses are about to have sex, but she asks him to smother her since she cannot take the pain from the sickness any longer. He can’t do it, so they just end up having sex. Milla goes outside one last time before dying next to Moses.
A flashback shows the four at the beach, with Milla asking Henry to take care of Moses when she is gone, to which he agrees.
The film starts with teenager Milla Finlay (Eliza Scanlen) standing on the platform waiting for a train. A slightly older boy, Moses (Toby Wallace), runs near the train tracks before the train arrives. Milla stays behind from her friends and talks to Moses. Her nose starts to bleed, and he gives her his shirt to stop the bleeding. In return, Moses asks for shelter since he has been kicked out of his house. Milla gives him a fifty and asks for a favor from him. Milla asks Moses to shave her head, as she is suffering from a terminal illness and is about to start chemo. Moses brings her to his house to do the job, but before he can finish, his mother and little brother Isaac (Zack Grech) come home. Although he tries to talk to them, his mother threatens to call the police, forcing Moses and Milla to leave.
Milla’s parents, Henry (Ben Mendelsohn) and Anna (Essie Davis), try to get intimate after a therapy session before they have to pick up Milla. Henry is a therapist and Anna takes drugs to cope with her daughter’s illness.
Milla brings Moses home to meet her parents. Anna admits to being put off by Moses being 23 while Milla is still a teen. He also has clear signs of drug use. Anna starts acting weird because she took Xanax and Zoloft and asks Moses an inappropriate question, embarrassing Milla. When she and Moses have a moment, Anna yells at them and tells him to leave. As he goes, Milla shows a clear interest in the boy.
As Milla prepares to begin chemo, she still goes through normal activities, like violin lessons with her tutor Gidon (Eugene Gilfedder). He helps her practice along with a neighbor boy named Tin Wah (Edward Lau). Meanwhile, Henry goes to see the fuss over a barking dog and a pregnant neighbor, Toby (Emily Barclay). They share a laugh after learning that Toby’s dog is also named Henry.
In the middle of the night, Moses breaks into the Finlay house to look for food and other resources. Anna catches him and calmly tries to talk him down, but Henry and Milla come in and witness the scene. Milla steps in to diffuse the situation and suggests that Moses stay for breakfast since it’s almost morning. Henry and Anna agree and have a pleasant chat with Moses over breakfast before Milla gets ready for school by unveiling her new wig, which Moses really likes. At school, another girl asks to try the wig on, which Milla agrees to, even though she is visibly put off by it. Later, she finds Moses outside the school, and she decides she wants to go to the formal with him.
Henry bumps into Toby again, and she asks him to help her change a lightbulb. He agrees to do so but gets shocked off the stool, though he is uninjured.
Moses goes to visit Milla later, despite Anna’s dissatisfaction. Milla sits by the pool while Moses swims for a little. She asks him to the formal and he accepts, but the moment is ruined when Milla starts to feel like she’s going to vomit. Milla asks Anna for the drugs, but Moses reveals he swiped them. Anna makes him leave, and Milla asks Moses if he only hangs out with her for the drugs and if he is making fun of her. He nods yes to the drugs but shakes his head for the second part. Regardless, Milla later finds Moses playing basketball with his friends and joins him as he goes to his job at the pharmacy.
Moses later takes Milla to a party organized by his brother. They dance together for a little bit, but another girl Moses knows appears and kisses him, to Milla’s dismay. She wanders through the party and encounters a mysterious woman that moves close to her briefly as they stare at lights. Milla dances with others for a bit until Moses finds her and takes her outside, where she throws up. He says he’s going to call her parents, but she tells him not to. He takes her to a nearby spot to recover and have a dance together. They then go outside to chat some more. At the same time, Henry and Anna go out onto the streets to search for Milla since she’s not answering her phone. Milla wakes up on the rooftop alone the next morning and later goes to the hospital.
Henry and Anna discuss Milla and Moses’s relationship, which Henry seems to be okay with, unlike Anna. She goes through a piano lesson with Gidon and has a heart-to-heart with him regarding Milla after Anna briefly snaps at him. Meanwhile, Henry goes to Toby’s house again, and after a chat, he impulsively kisses her. He immediately regrets it even though she didn’t mind it. Henry goes home and sits with regret over it, and although he doesn’t outright say it, Anna seems to understand but forgives him. Henry worries that they are losing Milla, so he goes to find Moses at the courts to confront him for abandoning Milla the other night. Moses tearfully tells him he did go back for her but things got messed up. Henry then invites Moses to stay with them even though he doesn’t like him, just because he wants Milla to be happy.
Moses stays with the Finlays and helps with things like making dinner. Things go well with him and Milla, and they even prepare to go to formal together until Milla finds out Henry is signing Moses’s drug prescriptions the same way he is with Anna. Milla rants to her parents and Moses, forcing him to leave because she thinks he doesn’t really care about her. He goes to his old house to see Isaac again, but he is once again driven out by their mother. He returns to Milla’s room and tells her he cares for her a lot and that he doesn’t know what he’ll do if she dies. They talk some more and spend the night together.
Milla’s parents host a birthday party for her, inviting all the neighbors. After the festivities, Milla and Moses prepare to have sex for the first time. She feels that now is a good time to die, and she asks him to smother her since she cannot take the pain from the sickness any longer. During sex, Moses tries but cannot go through with it. They continue to have sex until they finish. Later that night, Milla wakes up and walks outside to look up at the sky one last time and listen to the birds.
In the morning, Moses wakes up next to Milla. He tries to leave but is asked by Anna if Milla is up. Moses doesn’t outright say anything, but Henry appears to already know what happened. Anna walks into Milla’s room to give her breakfast but finds that she is dead. As she comes out ready to yell at Moses, he insists that she was already dead when he woke up. Anna breaks down and Moses holds her, while Henry goes into the bedroom to kiss his daughter one last time.
The final scene is a flashback showing Moses and the family at the beach. While Milla is taking Henry’s picture, she asks him to take care of Moses when she is gone, and Henry agrees. She then takes a lovely photo of her parents together.