The book opens in 2007 as Will Traynor is leaving his girlfriend, Alicia, in bed and heading out the door for his job as a high-powered financier. Will decides not to take his motorbike, a thrill that he normally loves, because it is raining hard. When Will steps into the road to hail a cab, he is hit by another cyclist and left unconscious.
The book then moves forward to 2009, introducing Louisa Clark, a 26-year-old woman with outlandish fashion sense living in the tiny village of Bishop’s Stortford in Essex, England. Louisa is walking home dejected after hearing that the Buttered Bun café where she has worked for six years has to close. Louisa knows that her family sorely needs the money, with her mother Josie stuck at home caring for Lou’s Granddad, a stroke victim, and Lou’s nephew Thomas, the son of Lou’s younger sister Treena. Lou goes to tell the news to her long-term boyfriend, Patrick, who is busy running laps as he trains for another triathlon. Patrick simply tells Lou to buck up and find another job.
Lou goes to the job center to find a new position, but hates most of the entry level experiences. Finally, the only job left is a six-month stint as a caretaker for a quadriplegic man. Louisa has no experience as a caretaker, but goes to meet Camilla Traynor for an interview. Camilla intimidates Lou, but somehow decides that Lou is the right person for the job of providing a friendly cheerful presence for her son. Lou then meets the man she will be caring for, Will Traynor. Will is completely dismissive at first, angry that his mother has hired yet another caretaker he does not want.
Lou does her best at work, making tea and doing small domestic chores as Will ignores her and sulks in his room. Will sometimes chats with the nurse, Nathan, who handles his physical needs, but never speaks to Lou. Lou keeps at it because her family needs the money even more now that Treena wants to go back to school. Two weeks into this jo, Will’s ex-girlfriend, Alicia, and former best friend, Rupert visit. They awkwardly tell Will that they are getting married after bonding in the wake of Will’s accident, and Will smashes all the pictures of his old life. Lou attempts to fix the pictures for Will, but he yells at her for trying to help. Lou shouts back at him that just because he has a disability doesn’t mean he gets to be an ass, and Will seems to find a new respect for Lou.
Lou and Will are now on better terms, and Will even lets Lou drive him to a doctor’s appointment, where Lou sees the scars on Will’s wrists left from Will’s attempted suicide. Soon after, Lou gets stuck at Will’s house during a snowstorm trying to care for Will as he struggles with the flu. After that night, Will and Lou become true friends. Lou shares more about her quiet life watching her family and her boyfriend pursue their hobbies and Will encourages her to stretch her horizons outside of their sleepy village. Will introduces Lou to foreign films and classical music, even letting Lou shave his beard and cut his scraggly hair. Despite these promising moments, Lou finds out that in six months is the date that Will has planned to end his life at an assisted suicide clinic in Switzerland.
The book then introduces Camilla’s perspective, explaining how helpless she feels in the face of her son’s depression at the prospect of such a limited life. Camilla busies herself with her job as a magistrate and her garden, ignoring her husband’s infidelity and her son’s discontent. After Will’s first suicide attempt, Camilla decides that she has to allow him to go to Dignitas and end his life in a less horrific manner.
Lou is profoundly uncomfortable with Will’s plan to end his life, but she says nothing as she goes into work. Will actually seems to be in a good mood for once, making Lou realize that she can’t be a part of his suicide. Lou leaves a letter of resignation for Camilla, but Camilla follows her home and convinces Lou to come back. Lou now has to convince Will to change his mind before the six months is up. Cracking under the pressure, Lou tells Treena about Will’s plan. Treena advises Lou to help Will see all the things he can still do from his wheelchair. Lou goes to the library and frantically starts planning excursions for Will.
The first excursion is to a horse race, a day that ends horrifically as Lou realizes how little she knows about the logistics of taking a wheelchair out in public places. Will stoically suffers through the day, telling Lou at the end that he has always hated horses anyway. Lou realizes that she has to take Will’s desires into account and remembers a time when her own power to choose was taken away. Lou was sexually assaulted by a group of university boys in a maze at a castle near her village, an experience that clipped Lou’s desire to leave her safe hometown and take risks in the real world. Lou decides to take a different approach with Will and plans a trip to the orchestra instead. This time, Lou fully researches the wheelchair accommodations and Will thoroughly enjoys himself. He is transported both by the beautiful music and the illusion of being out on a date with a girl in a pretty red dress (Lou).
Though Lou feels more secure than ever in her job, her home life is quickly changing. Patrick has started to notice the distance between him and Lou, while Treena has moved back to university with Thomas. As Will and Lou grow even closer, Lou invites Will to her parents’ house for her birthday dinner. Will fits easily into Lou’s family, charming Lou’s parents but putting Patrick on edge. The situation only worsens when Lou is indifferent to Patrick’s gift of a necklace but absolutely adores Will’s gift of striped bumblebee tights. Patrick starts to act more possessive towards Lou, but Lou remains focused on helping Will as much as possible.
As the weeks go by, the news is full of debates over the right to die while Lou’s family deals with their own bad news that Lou’s father has lost his job. In all the shuffle over beds when Treena comes home from university on weekends, Lou’s parents end up sleeping on the couch. Lou starts to consider other places to stay so that everyone can get a good night’s sleep. Will offers to let Lou stay in his spare room, and continues to tell Lou that she needs to search for more out of her life. Lou joins quadriplegia support chatrooms looking for excursions for Will and plans events for every day that Will feels well enough to leave the house. On one of these outings, Will convinces Lou to get a tattoo. She gets a small bumblebee, while he tattoos the date of his accident on his foot.
With only eight weeks to go before Will’s appointment at Dignitas, Lou is starting to despair over all the things that Will can’t do because of his wheelchair. She gets no rest at home either, as the sleeping arrangements in the cramped Clark household get no better. Patrick half-heartedly offers to let Lou move in with him and Lou reluctantly agrees. She tells Will how uncomfortable she is, and shares that her father is now unemployed. Will replies distantly that his offer of the spare room is still available, if Lou ever needs it. Will then gets Lou’s dad a job as the head of maintenance at his family’s castle. Lou’s dad is ecstatic, but Lou feels uncomfortable. She calls Will, wondering why he did something so nice when he seems angry with her over Patrick. He simply replies that now she can pursue her own interests without worrying about her family.
With seven weeks to go before Will’s deadline, Will meets with a will attorney. Camilla and Lou had started to believe that Will would change his mind, but it is clear that he is still working towards his plan to go to Dignitas. Camilla tells Lou to plan a big last trip for Will as a last attempt to change his mind. Lou continues to avoid Will as much as possible during the day, until he finally forces her to go for a walk with him to the castle maze. At Will’s prodding, Lou attempts to make it through the maze, but has a panic attack at the memory of the assault there six years ago. Will comes to lead Lou out and she comes clean about her secret, finally letting go of the guilt she has carried for years.
Unexpectedly, Will asks Lou to accompany him to Alicia and Rupert’s wedding. Will is on his best behavior while Lou accidentally gets drunk. Lou then asks Will to take her for a spin on a wheelchair on the reception dance floor and the two enjoy a beautiful night together before staying over in a hotel, where Lou convinces Will to go on one last trip with her. Camilla is furious that Will stayed out without telling her, but Will is adamant that he is still an adult and can make his own choices. Lou gets to work planning the trip of a lifetime for Will.
The book moves to the perspective of Nathan (Will’s nurse), as he explains that everyone could tell that Will and Lou had crossed some boundary at the wedding. Nathan is skeptical of the trip idea, but willing to do anything to help Will and Lou. He agrees to go along.
Lou tells Patrick that she can’t go along with him to a big triathlon in Norway because she has to go on the trip with Will. Patrick is angry and upset, so Lou goes to talk to her sister while he cools off. Treena helps Lou realize that she is much more interested in Will than she has been in Patrick for years. When Lou goes home to Patrick’s house, Patrick tries to apologize until he sees the plans that Lou has made for Will. Unable to accept that Lou is essentially going on a honeymoon with another man, Patrick asks Lou to move out.
Steven, Will’s father, takes over the narrative to tell how Lou moved into Will’s house. Steven is highly in favor of the trip that Lou has planned, even if having a quadriplegic son is making it hard for him to leave his dysfunctional marriage with Camilla for his mistress Della. Still, Steven is optimistic that this trip will change Will’s mind—until Will gets pneumonia and everything has to be cancelled.
Lou is shattered by the sight of Will weak in the hospital, and incredibly disappointed that Will’s health has made their last trip impossible. At the advice of Nathan, Lou quickly puts together a calmer resort trip to Mauritius. Lou is deeply worried during the flight and the first two days of the trip over Will’s fragile state, but Will soon begins to come back to life in the beautiful beach sun. Will, Lou, and Nathan swim and eat and generally make merry for nine days. Lou even tries scuba diving, unable to believe that she was once too scared to do any of these marvelous things. The last day, Lou spends the night in Will’s hotel room and Will confesses that he is planning to commit suicide. Lou tells him that she has known for months and that she has been attempting to change his mind. Furthermore, Lou tells Will that she loves him. Will tells Lou that he loves her too, but it is not enough to change his mind. He then asks Lou to come to Switzerland with him to say goodbye. Crushed and enraged, Lou refuses and doesn’t talk to Will for the rest of the trip home.
The novel switches to Katrina (Treena’s) perspective, telling how Lou returned to their parent’s house looking ill. Katrina lets Lou mope, but tells her to wake back up when Lou is accepted to a university to study fashion. At dinner, Lou finally tells their parents about Will’s plan to end his life. Lou’s mother is aghast and forbids Lou to have anything to do with it, but Lou realizes that she has to go be with Will one last time. Katrina helps Lou get to the airport for the last plane to Switzerland before Will’s appointment.
As Lou steps into Will’s room at Dignitas in Switzerland, she feels oddly relieved. The two share one last kiss before Will drinks the lethal solution that will end his life. Legal council is unable to find any wrong doing on the part of Will’s family or Lou in this matter, even though the newspapers spin the story as another atrocious episode in the right to die debate. Lou decides that she has to keep living—she takes the money that Will left her and travels to Paris, as Will had asked her to do. With Will’s support and financial help, Lou is on course to finally live her life to the fullest for the sake of both her and Will.