Hazel Grace Lancaster (Shailene Woodley) is an intelligent and witty teenager living in Indianapolis, who has terminal thyroid cancer that has since spread to her lungs. Believing she is depressed, Hazel's mother Frannie (Laura Dern) urges her to attend a weekly cancer patient support group to help her make friends who are going through the same thing.
One week, Hazel meets Augustus Waters (Ansel Elgort), a charming teenager who lost a leg from bone cancer years earlier but has since been cancer-free. He invites Hazel to his house and she accepts, where they bond over their hobbies and agree to read each other's favorite book. Hazel recommends An Imperial Affliction, a novel about a cancer-stricken girl named Anna that parallels Hazel's experience, and Augustus gives Hazel Counter Insurgence. They keep in touch via text over the weeks that follow and grow closer. After Augustus finishes the book, he expresses frustration with its abrupt ending (it ends in the middle of a sentence). Hazel explains that the novel's mysterious author, Peter Van Houten (Willem Dafoe), retreated to Amsterdam following the novel's publication and has not been heard from since.
Weeks later, Augustus tells Hazel that he has traced Van Houten's assistant, Lidewij (Lotte Verbeek), and has corresponded with Van Houten by email. Hazel then writes to him to find out more about the novel's ambiguous ending and Van Houten replies that he is only willing to answer her questions in person. Overwhelmed and excited, Hazel asks her mother if she can travel to Amsterdam to visit him, but Frannie rejects it because of financial and medical constraints. Augustus suggests that she use her "cancer wish" since children and young adults with life-threatening illnesses receive one arranged experience of their choice, but Hazel explains that she already used hers to visit Disney World when she was younger. Augustus and Hazel go on a picnic date and soon begin to fall in love. Augustus also surprises Hazel with tickets to Amsterdam after using his wish on her. However, days before the trip, Hazel suffers from pleural effusion and is sent to an intensive care unit (ICU). Although initially concerned, her doctors eventually agree to allow the trip, since they expect that she will soon become incapable of doing anything at all.
Hazel and Augustus arrive in Amsterdam and are presented with reservations at an expensive restaurant, pre-paid for by Van Houten. During the meal, Augustus confesses his love for Hazel. The following afternoon, they get the bus into the city and head to Van Houten's house, but are soon shocked to find he is a mean-spirited alcoholic; Lidewij arranged the meeting and their dinner on his behalf without him knowing anything about it. Angered by his assistant's actions, he taunts Hazel for seeking serious answers to a piece of fiction and belittles her medical condition. She leaves, utterly distraught. On their way back to the hotel, Lidewij invites them to go sightseeing to make up for their ruined experience. The three visit the Anne Frank House, where Hazel struggles to climb the house's many stairs. At the end of the tour, Augustus and Hazel kiss to the applause of many fellow tourists. They spend that night together in their hotel and have sex for the first time. The next day while out in the city, Augustus tells Hazel that his cancer has relapsed, has spread throughout his body and is terminal. Hazel is heartbroken, expressing how unfair life can be.
After their return to Indianapolis, Augustus' health worsens each week. Hazel receives a desperate call from him late at night after he tries to get a new pack of cigarettes at the gas station. He is taken to the ICU for a few days and realizes he is close to death. Augustus invites his blind best friend Isaac (Nat Wolff) and Hazel to his pre-funeral, where they deliver eulogies that they have both prepared. Hazel tells him she would not trade their short time together for anything, since he "gave me a forever within the numbered days."
Augustus dies eight days later. At his funeral, Hazel is astonished to find Van Houten in attendance. He tells her he maintained correspondence with Augustus after Amsterdam and that Augustus had demanded he attend his funeral to make up for the spoiled trip. He then tells Hazel that his novel is based on the experiences of his daughter Anna, who died from leukemia at a young age. Van Houten tries to tell Hazel about the fate of Anna's mother; he gives Hazel a piece of paper. Hazel, still upset with his behavior in Amsterdam, crumples up the paper and asks him to leave. Later, talking with Isaac, Hazel learns that Augustus had asked Van Houten to help him write a eulogy for her. She retrieves the crumpled paper and reads Augustus' words, which state his acceptance of death and his love for Hazel. Hazel lies on her back on her lawn looking up at the stars, smiling as she remembers Augustus and says "Okay."
Output: What illness is Hazel suffering from?