NOTE: This spoiler was submitted by Susan C
The movie starts with Justin (Justice Smith) waking up in bed and setting his smartphone alarm to 11 pm and 1150pm.
The scene cuts to a high school where the main character, Rhiannon (Angourie Rice), is talking about how she's been texting her boyfriend Justin a lot and he never texts back. She sees Justin and runs up to him, asking him why he didn't respond to any of her texts, and apologizing for texting so much. He hesitates for a second before answering her. Rhiannon tells him she wants to play hooky, skip school, and just spend time with him today. They skip school and have a great day in the aquarium, playing on the beach, and just generally having fun.
As they're getting ready to go home, Rhiannon tells him about her father; she's never talked to anyone about her father before. She tells Justin that one day he came home and told them he'd gotten a big promotion; booked an entire theater for the family so they could celebrate; then it turned out instead of a promotion, he'd been fired and had a meltdown. Now, her father spends his days painting, and her mother has to work two jobs. Justin listens and is sweet.
He drives her home, and she tells him it was a perfect day. He hesitates and tells her that not every day is going to be like this. She stops him and tells him she wants to end today on a good note. They kiss, and she tells him it's so much better kissing him when he doesn't smoke. He tells her he'll keep that in mind.
The next morning, a redheaded girl wakes up and looks behind the wall. She says "Amy" under her breath, and sets her smartphone alarm for 11 pm and 1150pm. At the high school, Rhiannon sees Justin. He's standing by his car, smoking. Amy (Jeni Ross) comes up to her and taps her on the shoulder, explaining that she is new to the school and wanted to ghost someone for a day. She asked if she could ghost Rhiannon. Rhiannon agrees.
In a lab class, Rhiannon introduces Amy to her friends Rebecca and Alexander (Amanda Arcuri and Owen Teague). Justin comes into the classroom looking for her and asks her if he'd gotten drunk yesterday. She tells him no, and asks him doesn't he remember. He unhappily tells her yesterday was a fog, and now he has a ton of homework he has to make up. He reminds her to go to a weekend party, tells her bye and leaves. She's upset that he had such a different reaction to yesterday. Amy notices and tells her she doesn't think her boyfriend treats her right. She reaches up and tucks a stray hair into Rhiannon's ear. Rhiannon's still upset, so she tells Amy to shadow Alexander for the rest of the day and goes.
Scene cuts to a boy, Nathan (Lucas Jade Zumann), waking up, and setting the alarm for 11 pm and 11:50 pm. He goes to his computer and searches for an address on the map. At the party, Justin is having fun and neglects Rhiannon. Nathan walks up to her, and they start having fun dancing. Justin notices them dancing and goes to claim Rhiannon. Nathan reassures him that he's gay, so he's not a threat. Then he suggests he's attracted to Justin, who looks a little creeped out and quickly excuses himself. After Justin leaves, Nathan asks Rhiannon if she'd like to go somewhere quiet to take a break from the party. They find a quiet spot, where Nathan then asks Rhiannon why she's with Justin. She says he's her type and describes that as "tall, slim, nice shoulders, has a connection." They talk for a long time, and Nathan ends up leaving late.
The next day, Rhiannon's friend is telling her about how a boy, Nathan, was found parked on the side of the highway and was now claiming he'd been possessed. Justin asks why she'd been hanging out with someone crazy like that. Rhiannon gets a text from a strange number asking her to meet, alone, at a coffee shop, saying they'd explain everything. She decides to go because of what happened with Nathan.
At the coffeeshop, a girl shows up and tells her that she was Justin the day they spent at the beach, and Amy the following day, and Nathan yesterday. Rhiannon is freaked out and disbelieving.
The following day, she gets another text from the same number, asking her to meet again. This time, it's a large Asian boy who's waiting for her. He gives her more details, and she starts to believe. He tells her he wakes up every day in a different body, always near the last body, and introduces himself as A. He doesn't know if he has parents, or where he's from. This has been his life (waking up in a different body) for as long as he's remembered. He spends half his time as a girl and tries to leave as little a trace as possible. He shows her an Instagram account he maintains that he says shows the faces of most of the people he's woken up in.
Later, she goes to visit Nathan at a church. Nathan tells her he was possessed by the devil and tells her about the Instagram account. No one believes him because he didn't have time to download any pictures before the password was changed. He recognizes her picture from the Instagram (A had posted a picture of her and "Justin/A").
At school the next day, Rhiannon meets A (as a girl), where A explains he ran out of time to delete the calls and Instagram from Nathan's phone, which is why Nathan thinks he was possessed. Rhiannon believes now and is upset that A kissed her as Justin. A tells her he'd never felt that way about anyone until he met her and that's why he acted so differently that time.
In Justin's bedroom later that day, Rhiannon asks Justin about their relationship. He asks her what she means, and she says she wants to know what he feels about their connection. Justin's nonplussed.
The scene cuts to Rhiannon meeting A in a library. Now he's a black guy named George. They talk more, and Rhiannon gets closer to A. They lean in for a kiss when they're interrupted by George's mother. A whispers to Rhiannon to run, and she escapes.
The next day, A wakes up in Rhiannon's body. He's excited and can't stop smiling, which her sister Jo notices. At school, Justin approaches her, and A blows up at him, telling him he doesn't appreciate her. A storms off, and then after he cools down, he's a little afraid of what Rhiannon will think tomorrow. A goes to Rhiannon's dad's studio and asks her dad why he paints. Her father replies that it's who he is. A writes a letter detailing what happened that day.
The next morning, Rhiannon wakes up. She finds Justin at school and tells him they need to take a break. He is upset at being dumped and leaves. She then finds A and tells A/female that she broke up with Justin and remembers what happened the day A was her. She tells A that he should let people keep more of the memories of that day he was in their bodies.
The scene cuts to Rhiannon riding in a truck with a guy. They are going driving to her uncle's vacation cabin, which is a three-hour drive away from home. They have a romantic day, and then A leaves with the truck. He promises to come back tomorrow. The next day, it rains, and she waits there all day. A never shows up. Rhiannon has to call her mother to ask her to pick her up from the cabin.
A wakes up in another body and realizes that the boy, Michael's, is supposed to be flying to Holland that day. He panics because if he ends up in Holland, that is where he will wake up tomorrow. He calls Rhiannon and asks her to rescue him. Rhiannon comes for him in her sister's car, knocking off the driver's side mirror while trying to escape Michael's mother. Rhiannon is upset that A left her alone at the cabin when he'd promised to come back. A explains he couldn't come because the girl whose body he woke up in was getting a lung transplant that day, and he hadn't woken up until the evening. He also wasn't allowed near any cell phones.
Rhiannon is in the car with her sister Jo, who asks her what's going on. Rhiannon tries to tell Jo about A, but Jo doesn't believe her. Jo tells Rhiannon she doesn't care what sort of weird polyamorous thing Rhiannon is doing, just leave her car out of it (Jo's mad about Rhiannon breaking the car mirror). At school, Rhiannon's friend Rebecca asks her about the rumors she heard of Rhiannon hooking up with a random guy who left her in the woods without a truck. Rhiannon blows up at Rebecca. Later that day, Rhiannon sees A, who's now occupying a suicidal girl's body (Kelsey). A tells Rhiannon that Kelsey has planned out her suicide in detail, and will probably try to kill herself as soon as A leaves her body. Kelsey's father works late and won't be home in time to stop Kelsey.
Rhiannon urges A to "push back" and try to stay in Kelsey's body long enough for the father to come home. The scene cuts to Kelsey's father coming home, and Kelsey (A) telling her father she needs help.
At school, Justin's friends are calling Rhiannon a slut. Rhiannon ignores them and meets A in the girls' locker room. A tells her he can't be with her after school this time because it's the girl's anniversary dinner with her boyfriend. At home, Rhiannon sees her mom and tells her that dad's changed, but so has she, so please can the two parents grow closer again.
A wakes up in Alexander's body (Rhiannon's lab friend), and tells Rhiannon what a great guy the real Alexander is. Rhiannon asks A to try to stay in Alexander's body for a while. A agrees, and there's a montage of days where Rhiannon and Alexander/A are having fun at school, kissing, holding hands. Rhiannon makes up with her friend Rebecca, who tells her she always thought Rhiannon and Alexander were perfect for each other.
Alexander's phone shows three missed calls from "mom," but A ignores it to be with Rhiannon. At night, Rhiannon and A are at Alexander's front door, and Rhiannon decides to come in. They enter the house where they see a huge "Happy Birthday Alexander" sign, and Alexander's family seated at the table with a cake, obviously having been waiting for him.
Alexander's mother goes up to see him and tells him that his aunts and she had spent the whole day cooking his favorite foods for him, at his request. She tells him he hasn't been himself lately, spending all his time with Rhiannon, and they love him but he should not to take his family for granted.
The next day, A meets Rhiannon and tells her to meet him that night at Alexander's house, as Alexander's family is going to be out of town that night. Rhiannon happily agrees, not noticing that A is quiet and seems like he wants to tell her something. That night, A tells her their relationship has to end, but that the real Alexander is perfect for her. Rhiannon is upset, but A tells her that it's not right. Alexander has a family who loves him, and it's not fair to Alexander for A to keep occupying his body. A also tells her their relationship is blocking Rhiannon from finding the right guy for her. A tells her to imagine what her life would be like 10 or 20 years from now when he could be waking up in a married man's body. He tells her that she will always be his first and only love, but he can't give her a normal life. Rhiannon finally accepts that she can't be with A, but wants to treasure the last three hours together.
At the end of the night, they are cuddling in bed, and Rhiannon asks if Alexander will remember what's happened. A tells her he will, to an extent. It's almost midnight, and A goes to sleep. Rhiannon kisses him, and then quietly leaves Alexander's bedroom.
The next morning, A wakes up as a rich black girl, Katie, and goes driving out of Katie's house. It's a new day.
At school, Rhiannon is putting things away in her locker, when Alexander comes up to her. He has a locker near hers. They put their things away in their lockers, and then Alexander asks Rhiannon, has anyone ever told you that you have a nice smile. Rhiannon flashes back to her first date with A (as Justin) when A told her she had a nice smile. The movie ends with Rhiannon and Alexander smiling tentatively at each other and walking down the school hallway together. The implication is that they will end up together.