In Miami, Zoya is in the hospital because doctors have found a black hole growing inside her chest. Since it has no cure, she only has one week left to live. The doctors tell Zoya’s husband Donald, her daughter Jayne, and her son-in-law to take Zoya home so she can spend her last days with the family.
During the trip home, the family tries to keep Zoya distracted with conversation and music, but Zoya is lost in her own thoughts. They keep trying to accommodate her, but she isn’t invalid and she mostly gets annoyed. The next day they go to see the publishers that have been in charge of all the couple’s science books, but they just think Zoya will get better and still want to discuss the last chapter of her latest book, which she hasn’t finished yet.
Next they visit the family lawyer to take care of the will and any other necessary paperwork for when the time comes. The family also takes Zoya to the beach and to a massage parlor to help her relax, but it doesn’t do much. Eventually Zoya visits her mother Sandra at the retirement home, but Sandra never speaks and only watches television.
Tired of this, Zoya goes outside to eat a fruit on a bench. At that moment another resident approaches her and Zoya warns her of incoming bird poop right before it falls. When the lady asks how she knew that, Zoya reveals that she’s been living through the last week over and over by taking the caplets she found as a child.
Every time she wakes up in the hospital and her family puts her through the same things, and she’s talked to this lady already. During the last day of the week, her family surprises her with a birthday cake and she has to pretend she didn’t see it coming. It’s at that moment that her nose starts bleeding, so she hides in the bathroom to take the caplet and reset time, instantly disappearing.
The next time she encounters the old lady, she saves her from the bird poop but doesn’t tell her how she did it. While visiting her mother, they watch the news of the last one-horned rhino on Earth arriving to Miami and Zoya tells her the rhino will die by the end of the week. It still doesn’t get a reaction from her mother, and Zoya is so annoyed that she doesn’t warn the old lady about the bird poop.
Tired of the same conversation, Zoya walks off and accidentally bumps into Paula, causing her to drop her things. Zoya is surprised to see Paula has been reading one of her old books and wonders where she got it, so Paula shows her that the retirement home has a library. Since most of these books were donated by the residents, Zoya finds many books that used to be hers during her youth because Sandra dropped them.
Paula explains she picked Zoya’s book because she’s working under a professor at a university lab and she’s studying time. Before Zoya can say more, Donald appears to take her home and Zoya brings the book with her. In the evening, Zoya wonders if there may be a chance for her to survive if she brings back her old research, crying as she complains about the routine.
Donald thinks spending her last few days inside a lab is a waste of time and takes her to the living room for her surprise birthday cake. When her nose starts bleeding, Zoya goes outside and calls Paula using the number on the book. She tells her she’ll find her soon to do something great then takes the caplet to reset the week.
When Zoya wakes up at the hospital, she tells Jayne and Donald to sign the paperwork while she gets ready to go home. However as soon as they’re gone, Zoya carefully sneaks out of the room and nobody sees her because they’re watching the game. She escapes through the fire exit and gets a cab, promising the driver she’ll pay when she gets home.
Minutes later, Zoya takes the hidden keys outside and enters her house, where she puts her caplets, books, and some clothing in a suitcase. After changing into fresh clothes she comes out ready to pay, but the cab is already gone. Next she goes to see Paula, who doesn’t recognize her because of the reset.
Zoya explains everything but Paula doesn’t believe her, hiding her hand and asking how many fingers she’s holding up to prove the story. Obviously Zoya fails the question, so she resets the week again and this time she does pay the taxi driver. The next time Paula test her knowledge, Zoya guesses many things, like all the hand gestures, the cat meowing, and Paula’s next few questions, meaning she’s been through this conversation many times already.
Finally believing her, Paula agrees to help and they go to the university while Zoya explains she tried figuring out how the caplets work thirty years ago, but life happened and she had to quit her research. She can only take one caplet at the time, if she takes another one now nothing happens because the other one needs to leave her system first. Her goal with this experiment is to fix her life so she can have more time and reach the greatness she wanted.
The lab and the equipment are quite old, but they’ll have to do for now. Zoya shares what she knows: the caplets don’t burn, melt, or dissolve. It’s almost like they were never really there and they’re constantly regenerating, as if existing in a state of limbo.
Paula wants to look at the regeneration itself to break it down, however Zoya points out that the process is happening at a subatomic level. Instead she thinks they should try to replicate it like she started to do in her youth. An argument ensues on how to proceed and Paula gets an idea, so she leaves the lab to get some help.
At that moment Zoya sees a call from Donald and ignores it. Feeling guilty, she tries to leave and is shocked to find Dulseberg, her old university professor. He’s happy to see her and invites her to his office, where he’s shocked to find Paula searching his desk.
When he freaks out, Paula says she’s working with Zoya and that she’s only “kind of” student here, which confuses Zoya. Dulseberg gets even angrier and blames it all on Zoya, remembering how he’d been impressed by her test scores and thought she’d be someone great, but she turned out to be a lazy and entitled student. The women are kicked out and Paula tries to convince Zoya not to take Dulseberg’s comments seriously.
However Zoya confirms he was right: she was lazy because she would pass the exams by resetting time. Then Paula brings out the box she stole from the professor’s office: it’s a nanoscopic man. An experiment was successful enough to shrink a person, but they weren’t able to stop the process so he continues shrinking to this day.
To work with him the duo goes to a cold dry-aging room because normal room temperature may bring bacteria and mold to the box. A hundred years for this man are just a few seconds in the normal world. Paula plugs the box in because the man has a transmitter in his suit, meaning he can make messages appear on a little screen and receive them as well.
His suit also has a particle detector, so they drop a caplet into the box for him to analyze. After the caplet shakes for a few seconds, lots of strange code appears on the little display and the computer connected to it. Paula looks at it and confirms Zoya’s right: the caplet is constantly changing, cycling through many different structures.
At the end of the day Zoya stays at Paula’s and shares that she found the bottle of caplets when she was twelve while walking in a golf course. It was just lying there and she took it because it had her name on it. There was nobody around, but she did hear a voice saying “you’ll change the world”.
The next few days the duo keeps on trying different methods to understand caplets, but they don’t make much progress especially since the old equipment keeps breaking. Zoya has to reset the week multiple times and escape the hospital every time to recruit Paula and start over. In a few resets Zoya does go home to be with her family.
When Jayne gets anxiety because she’s stuck teaching music to kids instead of being a composer, Zoya insists she should be playing in her free time until she gets her big break. This is based on her own childhood, because kid Zoya used to promise her dad that she’d be a scientist just like him. Resets continue to happen and so does the research.
The duo isn’t making any progress, and Zoya is scared that even with all the time in the world she won’t be able to succeed. One morning before Zoya arrives to recruit Paula, her real situation is revealed. It turns out the professor she was supposed to work under suddenly took a sabbatical and it was too late for her to choose another one this year.
Many resets later, Zoya and Paula wait for a little explosion to happen in the lab while discussing other options. Paula thinks it’s strange that Zoya never got any support for her research in the old days, so Zoya admits that after graduation she didn’t join a science program in Europe like her fellow students. Donald had told her “to be sure it would make her happy”, which had made Zoya realize she didn’t actually enjoy experimentation, she only wanted to figure the caplets out.
Then Paula asks about her old research and Zoya remembers it was left behind with her mom’s things. At that moment Zoya’s nose starts bleeding so she takes the caplet to reset the week. She goes through the usual process of recruiting Paula and they go to the retirement home to search her mom’s old boxes.
Sandra kept her own psychology papers and a newspaper article about research at NASA by Zoya’s ex Mark, but she didn’t keep any of her daughter’s work. While wondering what to do next, a nurse tells Zoya that Donald is around desperately searching for her in tears. However when Zoya tries going after him, he’s already gone.
On her way back, Zoya thinks about the day she told Donald she wasn’t joining the Europe program. He actually had wanted her to go since it was a great opportunity, and only told her to do what makes her truly happy after she said she had no intention of changing her mind. A few resets later, the lack of emotional support is taking its toll on Zoya.
She misses her family and it’s getting hard to leave them behind over and over. Meanwhile her family keeps getting the surprise cake ready but she never shows up and Zoya wonders if they’re just standing there through the resets waiting for her. After hundreds of more resets, Zoya realizes she’s been stuck in another dull routine and announces they’ve finally tried everything, so there’s no point in continuing.
Paula insists they shouldn’t give up and tells Zoya to ask Mark for help, but Zoya just wants to be with her family. Now it’s Paula’s turn to snap, pointing out she’s risked her job and stole the little man just for a lady that showed up at her apartment one morning. After revealing she also wants to go back in time to fix her life, Paula runs out of the room.
Zoya follows her out and Paula gives her back the caplets. She didn’t dare to take one because she was afraid she would get the black hole inside her body too. Paula wants to go back because when she was fifteen she took her parents’ car out without permission and drove over a nail.
She put the car back without a word, thinking the parents would find the nail and remove it. However they didn’t see it and the tire blew up, killing them. Wanting to help Paula, Zoya announces she’ll find Mark.
That night Zoya shares that she found the caplets a week after her dad died and she tried to go back to save him, but she always woke up a day after his death. When Zoya mentions failing to be great like her dad hoped, Paula points out she wrote plenty of books and that’s achieving a lot. The moment is interrupted by Zoya’s nose bleeding and she resets the week, disappearing from Paula’s room.
After waking up, Zoya gathers her things and goes to see Dulseberg instead of Zoya. She goes on a rant about what he thinks of her and admits she can indeed be lazy or impatient, but at least she’s trying and right now she needs Mark to achieve the next step. Impressed, Dulseberg gives her Mark’s address.
Afterward Zoya goes to the airport and while waiting for her plane, she thinks about the last time she saw Mark. They both attended the class reunion and their conversation had been very awkward because they belonged to different worlds, in fact Zoya felt Mark’s comments were demeaning. When Zoya finally makes it to Mark’s house, it’s his son Chris who opens the door with terrible news: Mark died.
He spent all his time working and didn’t eat or sleep, which completely ruined his health. Zoya is taken to Mark’s office and among all his research and awards, she’s shocked to find her own old notebooks. Chris admits he hates that room because Mark always said his work would make his son proud, but Chris only wanted a father.
Then Zoya offers a hug to comfort him. Moments later Zoya goes through her old research and notices she used to write Donald’s name on the pages. She thinks about their old dating days and understands what’s most important to her, so she finally listens to all the messages in her voicemail.
Joyce and Donald sound more and more desperate with each message because they can’t find her. In the last ones they’re crying and begging her to come back because they don’t want her to die without seeing her one last time. Zoya has a breakdown as her nose starts bleeding, and when she looks down she sees the black hole growing in her chest.
She desperately searches for her caplets to reset time one last time. When she wakes up, Zoya runs out of her room to hug her daughter and apologize. During the trip home, she behaves more friendly and gladly joins the conversation.
That night she does the dirty with Donald and asks him if he believes they’ve lived a good life; he says yes with no hesitation. The next few days Zoya is more energetic while participating in activities with her family. She signs her will after adding a note to donate all her books to the retirement home, she brings Donald to the massage parlor to hold hands during it, and has a great time at the beach with her family.
When she visits Sandra, she takes her to see the rhino before it dies. On the last day, Zoya visits Paula to hand her the caplets and her research. She’s understood that being great means knowing when to pass your work to the next generation instead of chasing glory.
Later Paula finds a little note in the notebook telling her who to contact in Princeton for support. That night Zoya happily enjoys the birthday cake with her family. This time her nose doesn’t bleed and she stays in the room, so Jayne brings her a present.
It’s an ultrasound revealing that Jayne is pregnant, and she says they’ll name the baby Zoya. As she cries in happiness, Zoya hugs her daughter but pulls back when her nose starts bleeding. She apologizes for not always being there for them and kisses Donald before telling everyone that she loves them.
Suddenly the scene freezes except for the clock ticking. Zoya disappears in a weird blur that represents her death and reappears in the past, telling her younger self the words she remembers hearing when she picked up the bottle.