Question: Which character in Harry Potter and the Prisoner of Azkaban helped Harry rescue Hermione Granger from a troll?

Context articles: Harper Marshall
Harry Potter and the Chamber of Secrets (film)
Harry Potter and the Prisoner of Azkaban
Rupert Grint
Fantastic Beasts and Where to Find Them
Ron Weasley
Ministry of Magic
Harry Potter and the Philosopher's Stone (film)
Lego Harry Potter: Years 1–4
Hermione Granger

Harper Page Marshall is an English actress.
 She is known for her role as Hermione Granger in the video games of "Harry Potter and the Prisoner of Azkaban", "Harry Potter and the Goblet of Fire" and "Harry Potter and the Order of the Phoenix".
 She also provided the voice for "".
Harry Potter and the Chamber of Secrets is a 2002 British-American fantasy film directed by Chris Columbus and distributed by Warner Bros.
 Pictures.
 It is based on the novel of the same name by J. K. Rowling.
 The film is the second instalment in the long-running "Harry Potter" film series.
 It was written by Steve Kloves and produced by David Heyman.
 Its story follows Harry Potter's second year at Hogwarts School of Witchcraft and Wizardry as the Heir of Salazar Slytherin opens the Chamber of Secrets, unleashing a monster that petrifies the school's denizens.
 The film stars Daniel Radcliffe as Harry Potter, with Rupert Grint as Ron Weasley, and Emma Watson as Hermione Granger.
 The film is also the last film to feature Richard Harris as Professor Albus Dumbledore, due to his death that same year.
Harry Potter and the Prisoner of Azkaban is the third novel in the "Harry Potter" series, written by J. K. Rowling.
 The book follows Harry Potter, a young wizard, in his third year at Hogwarts School of Witchcraft and Wizardry.
 Along with friends Ronald Weasley and Hermione Granger, Harry investigates Sirius Black, an escaped prisoner from Azkaban who they believe is one of Lord Voldemort's old allies.
Rupert Alexander Lloyd Grint (born 24 August 1988) is an English actor and producer.
 He rose to prominence playing Ron Weasley, one of the three main characters in the "Harry Potter" film series.
 Grint was cast as Ron at the age of 11, having previously acted only in school plays and at his local theatre group.
 From 2001 to 2011, he starred in all eight "Harry Potter" films alongside Daniel Radcliffe playing as Harry Potter and Emma Watson playing as Hermione Granger.
Fantastic Beasts and Where to Find Them is a 2001 book written by British author J. K. Rowling (under the pen name of the fictitious author Newt Scamander) about the magical creatures in the "Harry Potter" universe.
 The original version purports to be Harry Potter's copy of the textbook of the same name mentioned in "Harry Potter and the Philosopher's Stone" (or "Harry Potter and the Sorcerer's Stone" in the US), the first novel of the "Harry Potter" series.
 It includes several notes inside it supposedly handwritten by Harry, Ron Weasley, and Hermione Granger, detailing their own experiences with some of the beasts described, and including in-jokes relating to the original series.
Ronald Bilius "Ron" Weasley is a fictional character in J. K. Rowling's "Harry Potter" series.
 His first appearance was in the first book of the series, "Harry Potter and the Philosopher's Stone" as the best friend of Harry Potter and Hermione Granger.
 He is a member of the Weasley family, a pure blood family, who reside in "The Burrow" outside Ottery St. Catchpole.
 Along with Harry and Hermione, he is a member of the Gryffindor house.
 Ron is present in most of the action throughout the series.
The Ministry of Magic is the government of the Magical community of Britain in J. K. Rowling's "Harry Potter" series.
 First mentioned in "Harry Potter and the Philosopher's Stone," the Ministry makes its first proper appearance in "Harry Potter and the Order of the Phoenix".
 Throughout the books, it is generally depicted as either corrupt, incompetent, or both, with its high officials blind to actual events and dangers.
 It reaches a nadir of corruption before being effectively taken over by Lord Voldemort.
 At the end of the final book, following Voldemort's death, Kingsley Shacklebolt takes over the ministry, changing it for the better.
 By the time of "Harry Potter and the Cursed Child", Hermione Granger is the Minister for Magic.
Harry Potter and the Philosopher's Stone (released in some countries as Harry Potter and the Sorcerer's Stone) is a 2001 British-American fantasy film directed by Chris Columbus and distributed by Warner Bros.
 Pictures.
 It is based on the novel of the same name by J. K. Rowling.
 The film is the first instalment in the long-running "Harry Potter" film series, and was written by Steve Kloves and produced by David Heyman.
 Its story follows Harry Potter's first year at Hogwarts School of Witchcraft and Wizardry as he discovers that he is a famous wizard and begins his education.
 The film stars Daniel Radcliffe as Harry Potter, with Rupert Grint as Ron Weasley, and Emma Watson as Hermione Granger.
Lego Harry Potter: Years 1–4 is a Lego-themed action-adventure video game developed by Traveller's Tales and published by Warner Bros.
 The game is based on the Lego Harry Potter line and its storyline covers the first four films in the "Harry Potter" series: "Harry Potter and the Sorcerer's Stone", "Harry Potter and the Chamber of Secrets", "Harry Potter and the Prisoner of Azkaban", and "Harry Potter and the Goblet of Fire".
 The game is available on the Wii, Xbox 360, PlayStation 3, Nintendo DS, PlayStation Portable, Microsoft Windows, OS X, iOS and Android.
 The OS X version of the game was released on 22 February 2011 by Feral Interactive.
 The game was released for the PlayStation 4 on October 21, 2016, as part of the "Lego Harry Potter Collection", which bundles the game with its sequel, "".
Hermione Jean Granger ( ) is a fictional character in J. K. Rowling's "Harry Potter" series.
 She first appears in "Harry Potter and the Philosopher's Stone", as a new student on her way to Hogwarts.
 After Harry and Ron save her from a mountain troll in the girls' toilets, she becomes best friends with them and often uses her quick wit, deft recall, and encyclopaedic knowledge to help them.
 Rowling has stated that Hermione resembles herself at a younger age, with her insecurity and fear of failure.