Argus Filch is the caretaker and (effectively) hall monitor in J. K. Rowling's Harry Potter. While he arguably does not act malliciously, and is not an evil character, Filch's attempts to enforce the letter of rules against activities such as being outside the dorms late make life very inconvenient for Harry and many of his friends.
Filch has a cat named Mrs. Norris. Mrs. Norris is hated by the students as well. If Mrs. Norris catchs a student putting one toe out of line, Filch will come, drawn by the mysterious power that conects him with his cat. It is the dearest ambition of many to give Mrs. Norris a good kick. Whenever Hagrid goes up to the school Mrs. Norris follows him everywhere, he can't get rid of her. Filch puts her up to it. Hagrid wants to introduce Mrs. Norris to Fang someday. Filch calls Mrs. Norris "my sweet."
For years Filch has been trying to bring the "old punishments" back, where students are hung by their hands in the dungeons for days, are whipped etc. In Harry Potter and the Order of the Phoenix when Dolores Umbridge took control of Hogwarts he got his wish breifly. Filch called Umbridge the best thing that ever happened to Hogwarts, making him the only staff member to take her side.
Filch and his cat are mutual mortal enemies with Peeves, whom they constandly wage war aganist. Harry and his friends sometimes get involved in this conflict, though they don't take sides, as neither charactors are very likable.
Filch is played by David Bradley in the films.
Filch was revealed to be a Squib in Harry Potter and the Chamber of Secrets, when he is caught by Harry trying to teach himself basic magic from a correspondence course. Also, many fans beilve that Mrs. Norris will play a larger role in the forthcomming books.
