Riley Aly Michalka records her visit with her doctor, Sean Hood who plays Dr. Morton, so her absent mother will know Riley has stage 3 oral cancer with a 10% chance of survival.
On a bus to Sequoia National Park, Ogden Dustin Milligan offers to drop her off after their chance encounter, and just before she exits his car, she kisses him.
Earlier the same day, Riley’s sister, Van Sophi Bairley, tries to sneak out to meet Riley but totals the car. Van reluctantly tells their father, Oscar Todd Lowe, that Riley is in Sequoia with lethal drugs.
Furious, Oscar phones his ex-wife and Riley’s mother, Bev Joey Lauren Adams, who shows no sympathy toward Riley’s latest “staged drama.” Bev’s new partner, Steve Demetri Martin, is equally unsympathetic. Steve and Bev, motivated to finalize Oscar and Bev’s divorce papers, agree to drive Oscar and Van to Riley’s location—just after Steve drives them all to his interview first.
Back at the hotel, Riley listens to Van’s voicemail and is upset to learn that Van won’t be joining her on her last day.
In the morning, Ogden finds Riley at the hotel’s pool where she shows him the effects of her oral cancer. He stays with her and also obliges to take her to the peak, the ironically named Hanging Rock.
It is not until Riley and Ogden reach a blocked road that she reveals to him that she’s taken lethal drugs and is running out of time. This frustrates them both. She steals his car and drives away leaving him behind, but Ogden, having memorized her phone number from earlier, calls and promises that he’ll stay with her until the end wherever she wants to go. Reunited, Riley teaches Ogden how to film her last moments but in doing so, they also film each other exploring and enjoying the park. During a brief rainstorm, they retreat to the car and Ogden plays the mandolin and sings an original song to her.
Afterwards, Ogden films Riley from afar as she approaches the Sherman Tree (General Sherman Tree), a tree believed to have healing powers. There, she meets Colin Lou Diamond Phillips, a man with AIDS who prays to the tree, by telling it his disease, why he wants to live, for how many years, and what he promises to do if he gets his wish. Riley doesn't ask for a specific number of years but she does ask to live to help Ogden’s songwriting.
Riley then collapses, but Ogden manages to drive her to the peak for her final moments. When Riley’s family arrives, they see Riley peacefully lying on Ogden’s lap.
Riley’s parents watch her videos in a hospital waiting room. Riley wakes up and Van asks her to stick around until Van is at least 18. The film ends with all of Riley’s family bickering, but reunited. While her family bickers, Riley receives a call from Ogden who sings her new lyrics to his song from earlier.
