Hermione first appears in Philosopher's Stone when she meets future companions Harry and Ron on the Hogwarts Express. She constantly annoys her peers with her knowledge. Harry and Ron initially consider her arrogant, especially after she criticises Ron's incantation of the Levitation Charm. They heartily dislike her until they rescue her from a troll, for which she is so thankful that she lies to protect them from punishment, and their friendship begins. Hermione's knack for logic later enables the trio to solve a puzzle essential to retrieving the Philosopher's Stone, and she defeats the constrictive Devil's Snare plant by conjuring fire.
Rowling said on her website that she resisted her editor's requests to remove the troll scene. "Hermione is so very annoying in the early part of Philosopher's Stone that I really felt it needed something (literally) huge to bring her together with Harry and Ron."
Hermione develops a crush on handsome new Defence Against the Dark Arts teacher Gilderoy Lockhart in Harry Potter and the Chamber of Secrets. During a morning confrontation between the Gryffindor and Slytherin Quidditch teams, a brawl nearly ensues after Draco Malfoy calls her a "Mudblood," an insulting epithet for Muggle-born wizards. She assembles the Polyjuice Potion needed for the trio to disguise themselves as Malfoy's housemates in order to collect information about the Heir of Slytherin who has reopened the Chamber of Secrets. However, she is unable to join Harry and Ron in the investigation after the hair plucked from the robes of Slytherin student Millicent Bulstrode (with whom Hermione was previously matched up during Lockhart's ill-fated Duelling Club) was actually that of her cat, whose appearance she takes on in her human form; it takes several weeks for the effects to completely wear off. Hermione is petrified by the basilisk after successfully identifying the creature through library research; though she lies incapacitated in the hospital wing, her information is crucial to Harry and Ron in their successful mission to solve the mystery of the Chamber of Secrets. Hermione is revived after Harry kills the basilisk, but she is devastated to learn that all end-of-year exams have been cancelled as a school treat.
Hermione gets a cat named Crookshanks, who takes to chasing Ron's pet rat, Scabbers. Before the start of term, Professor McGonagall secretly gives her a Time-Turner, a device which enables her to go back in time and handle her heavy class schedule. Much tension comes into play between Hermione and her two best friends; Harry is furious with her because she told McGonagall that he had received a Firebolt, which was confiscated to be inspected for traces of dark magic. Ron is irritated because he feels Crookshanks is responsible for Scabbers' disappearance.
While filling in for Remus Lupin in one Defence Against the Dark Arts class, Severus Snape labels Hermione "an insufferable know-it-all" and penalises Gryffindor after she speaks out of turn in her attempt to describe a werewolf when no one else does. She correctly deduces Lupin's secret after completing Snape's homework assignment from the class, while Crookshanks proves vital in exposing Scabbers as Peter Pettigrew, a friend of James and Lily Potter who revealed their whereabouts to Lord Voldemort the night of their murders, and was able to wrongly implicate Sirius Black (revealed to be Harry's godfather) in the Potters' deaths. The Time-Turner enables Hermione and Harry to rescue Sirius and the hippogriff Buckbeak.
Hermione is horrified by the cruelty she witnesses to house-elves and founds S.P.E.W. as an effort to gain basic rights for the elves. She is Bulgarian Quidditch prodigy Viktor Krum's date at the Yule Ball in Goblet of Fire.[17] The proper pronunciation of her name (Her-my-oh-nee) is interjected into the plot when she teaches it to Krum; the best he can do is "Herm-own-ninny," but she has no problem with it.[6] She later gets into a heated argument with Ron after he accuses her of "fraternising with the enemy" in reference to her friendship with Krum. She supports Harry through the Triwizard Tournament, helping him prepare for each task. Near the end of the term, she stops fraudulent tabloid reporter and unregistered Animagus Rita Skeeter, who had published defamatory material about Hermione, Harry, and Hagrid during the Triwizard Tournament, by holding her Animagus form (a beetle) captive in a jar.
Hermione becomes a Gryffindor prefect along with Ron, and befriends Luna Lovegood, but their friendship gets off to a rocky start after Hermione chastises Luna's father's publication: "The Quibbler's rubbish, everyone knows that." She also lambastes housemate Lavender Brown for believing the Daily Prophet's allegations of Harry fabricating stories of Voldemort's return. Later, with Luna's assistance, Hermione blackmails Rita Skeeter into interviewing Harry for an upcoming issue of The Quibbler. Attempts to ban the magazine from Hogwarts are futile as the story spreads quickly through the school. One turning point in the series is when she conceives the idea of Harry secretly teaching defensive magic to a small band of students in defiance of the Ministry of Magic's dictum to teach only the subject's basic principles. Hermione gets an unexpectedly huge response, and the group becomes the nascent Dumbledore's Army. She is involved in the battle in the Department of Mysteries and seriously injured by Death Eater Antonin Dolohov, but makes a full recovery.
New Advanced Potions professor Horace Slughorn invites Hermione to join his "Slug Club," and she helps Ron retain his spot on the Gryffindor Quidditch team when she secretly jinxes Cormac McLaggen, causing him to miss his last save attempt during Keeper tryouts. Hermione's feelings for Ron continue to grow and she decides to make a move by inviting him to Slughorn's Christmas Party, but he romances Lavender instead in retaliation for Hermione having kissed Krum. She attempts to retaliate by dating McLaggen at the Christmas party, but her plan goes bust and she abandons him midway through the party. Ron and Hermione continually feud with each other until he suffers a bout of near-fatal poisoning from tainted mead, which frightens her enough to reconcile with him. Following Dumbledore's death, Ron and Hermione both vow to stay by Harry's side regardless of what happens. A minor subplot in the book is that Hermione and Harry form a rivalry in Potions, as Hermione is used to coming first in her subjects and is angered that Harry outperforms her undeservingly by following tips and different instructions written in the margins of Harry's potions book by the previous owner.
In the seventh and final book, Hermione is invaluable in Harry's quest to destroy Voldemort's remaining Horcruxes. Before leaving on the quest, she helps ensure the safety of her parents by placing a memory charm on them, making them think they are Wendell and Monica Wilkins, whose lifetime ambition is to move to Australia. She inherits Dumbledore's personal copy of The Tales of Beedle the Bard, which allows her to decipher some of the secrets of the Deathly Hallows. Hermione's spell saves her and Harry from Lord Voldemort and his snake Nagini in Godric's Hollow, although the ricochet snaps Harry's wand. When she, Ron, and Harry are captured by Snatchers, who are on the hunt for Muggle-borns under the Ministry's orders, Hermione disguises Harry by temporarily disfiguring his face with a Stinging Hex. She also attempts to pass herself off as former Hogwarts student Penelope Clearwater and a half-blood to avoid persecution, but is later recognised and taken to Malfoy Manor. Because of Hermione's Muggle-born status, Bellatrix Lestrange tortures her with the Cruciatus Curse in an attempt to extract information on how Hermione, Harry, and Ron came to possess Godric Gryffindor's sword (which was supposed to be safe in the Lestranges' vault in Gringotts). Even under the torture of the Cruciatus Curse, Hermione is able to use her quick thinking to lie to Bellatrix that the sword is a fake. When the others are able to escape their cell, Bellatrix threatens to slit Hermione's throat. Hermione, Harry, Ron and the other prisoners being held in Malfoy Manor are eventually rescued by Dobby.
Hermione later uses Polyjuice Potion to impersonate Bellatrix when the trio attempt to steal Hufflepuff's cup from Gringotts. She, Harry and Ron join Dumbledore's Army in the Battle of Hogwarts, during which Hermione destroys Hufflepuff's cup in the Chamber of Secrets with a basilisk fang, eliminating another Horcrux. Hermione and Ron also share their first kiss in the midst of the battle. In the final battle in the Great Hall, Hermione fights Bellatrix with the help of Ginny Weasley and Luna Lovegood. However, the three of them are unable to defeat Bellatrix, and stop fighting her once Molly Weasley orders them to back off.
Nineteen years after Voldemort's downfall, Ron is married to Hermione and they have two children: a daughter, Rose, and a son, Hugo. She is the only one of the trio to complete her seventh year, after which she begins her post-Hogwarts career by working in the Department for the Regulation and Control of Magical Creatures, where she is instrumental in greatly improving the lives of house-elves; she later moves higher up in the Department of Magical Law Enforcement while ensuring the eradication of oppressive pro-pureblood laws. Rowling stated in a webchat that Hermione found her parents in Australia and relieved them of the memory charm she had placed on them.
