Short answers, pulled from the story.
Session 9 was filmed on location at the actual Danvers State Hospital in Danvers, Massachusetts, a then-disused psychiatric institution. The production was restricted to certain confined areas of the building, which still contained asbestos, collapsing floors, and abandoned medical equipment.
Session 9 was inspired by the Richard Rosenthal case, a 1995 murder in Boston in which Rosenthal killed his wife after she accidentally burnt his dinner, then cut out her heart and lungs and placed them on a stake in his backyard. Director Brad Anderson grew up in Boston and used the case as a psychological blueprint for the film's central character.
Session 9 earned $76,493 during its opening weekend in Boston, Los Angeles, and New York City, and ended its American theatrical run with a total gross of $378,176. The film performed better internationally, earning $1.2 million in foreign markets.
Session 9 was directed by Brad Anderson, who co-wrote the screenplay with Stephen Gevedon. Before Session 9, Anderson had directed only romantic comedies: Next Stop Wonderland in 1998 and Happy Accidents in 2000. Session 9 was his first horror film.
The tapes are nine recorded therapy sessions with a former hospital patient named Mary Hobbes, who had dissociative identity disorder. The final tape reveals that a personality called Simon was responsible for Mary murdering her family, and the film closes on Simon's line: "I live in the weak and the wounded, Doc." Whether Simon is a psychiatric alter ego or a malevolent spirit remains intentionally unresolved.
Session 9 built its cult reputation primarily through DVD rentals and word of mouth after its limited 2001 theatrical release. Bloody Disgusting ranked it fifth on its list of the best horror films of the 2000s, and the film was picked up by Netflix by 2021. A novelization by Christian Francis was published on the 4th of October 2024.