The character Hermione is played by Emma Watson in the Harry Potter movies.
Harry and Ron do not like Hermione initially; in Harry Potter and the Philosopher's Stone, while still on the Hogwarts Express, Ron hopes that he doesn't end up in the same house as her. They later warm to her: she lies to Professor McGonagall to keep them out of trouble, after they save her from a troll attack—she had been in the bathroom, crying over a comment Ron had earlier made about her not having friends. She helps Harry to get past the Devil's Snare and the Potions puzzle when he seeks to stop the theft of the philosopher's stone.
Her parents are both muggles, and in Harry Potter and the Chamber of Secrets she is petrified by the basilisk while researching a hunch; this information later helps Harry and Ron to save Ron's sister, Ginny.
In Harry Potter and the Prisoner of Azkaban, Hermione is again estranged from her friends, first when she is suspicious about Harry's Christmas gift, a Firebolt broom, and reports it to Professor McGonagall, who confiscates it; and again when Ron accuses her cat, Crookshanks, of killing his rat Scabbers. While estranged from her friends, she helps Hagrid to prepare for the court case against his hippogriff, Buckbeak, though these efforts are unsuccessful. She and Harry later help the hippogriff to escape.
Hermione starts to relax in that book, and after taking a dislike to Professor Trelawney and her subject, Divination, she quits the class after having made an attempt to study all subjects available to third year students. To do this, she required the use of a Time Turner, which she and Harry used in their rescue of Buckbeak.
In her fourth year, in Harry Potter and the Goblet of Fire, her attention is drawn to the poor quality of life of house-elves. She makes the decision to start an organisation, Society for the Protection of Elvish Welfare, which becomes known by its unfortunate acronym. She begins a relationship with Viktor Krum, the Triwizard champion from Durmstrang, and vows vengeance against Rita Skeeter, a reporter who has been spreading lies about both Harry and herself. She later determines that Rita is an illegal animagus, and traps her. She is friends with Ginny.
She continues S.P.E.W. in Harry Potter and the Order of the Phoenix, knitting items of clothing for the elves, in the hope of freeing them (though the house elves refuse to clean Griffindor Tower because of this, and the task is left to Dobby). Her capture, and subsequent blackmail of Rita Skeeter proves useful when they need an article stating the return of Lord Voldemort. Hermione also came up with the idea for Dumbledore's Army. She was also involved in the battle in the Department of Mysteries.