Furnace is a 2006 horror film written and directed by William Butler. It stars Danny Trejo, Michael Pare, Tom Sizemore, Ja Rule, and Paul Wall.
A group of prisoners are assigned to assist in the re-opening of an old prison's closed wing. They find that the furnace room in the wing is the location of a murder, and the victim's spirit seeks death of those who enter the room.
The original script for Furnace was written by Anghus Houvouras, and the project was brought up to director William Butler, who thought that the story was reminiscent of the 1988 film Prison. Butler signed to direct, and he and his writing partner Aaron Strongoni collaborated to polish the script to meet Melee Entertainment's budgetary concerns. The rewriting lasted six months and changed the story substantially. Butler said of the change, "This of course was no reflection on Anghus, but instead the team of people at Melee that sort of took the film in another direction."