"All Hell Breaks Loose" is the joint title for the twenty-first and twenty-second episodes of the second season of the television series Supernatural. It is a two-part season finale, with "Part One" being first broadcast on The CW on May 10, 2007, and the second part airing the following week on May 17, 2007.

The episodes are notable for wrapping up many storylines running throughout the first two seasons, but at the same time opening up many new ones. The narrative follows series protagonist Sam Winchester ( Jared Padalecki) as he is abducted by series villain Azazel ( Fredric Lehne) and sent to an abandoned town, where Azazel intends to find a leader for his demon army by having Sam and other psychic children like him fight to the death. Sam is eventually killed, but is resurrected after his brother Dean Winchester ( Jensen Ackles) sells his soul. The sole survivor, Jake ( Aldis Hodge), is sent by Azazel to a cemetery protected against demons, where he opens a gateway to Hell. At the end of the episode, Azazel is finally killed by Dean with the mystical Colt revolver, but not before hundreds of demons are released into the world.

Many problems and changes occurred during the production process. "Part One"'s setting was altered after production learned of a pre-existing set previously used for the Western television series Bordertown, and the choice of location in turn influenced the type of supernatural monster that was featured. The once-epic script of "Part 2" had to be greatly toned down due to budgetary reasons, with bad weather conditions forcing the episode's climax to be filmed on a soundstage rather than on location. The scenes featuring the return of John Winchester ( Jeffrey Dean Morgan) had to be filmed weeks in advance using blue screen due to the actor's limited availability.

Despite receiving season-low ratings, the episodes garnered positive reviews from critics, who praised both the writing and the decision to end the main storylines. The performances of Fredric Lehne and Ona Grauer were also applauded, with Jessica Harmon gaining a Leo Award nomination for her role.

A major theme throughout the series is a "war of demons against humanity", with the potential for it being hinted at during the first two seasons. ^[1] It finally started at the end of the second season. ^[1] Following the "epic kind of scope" associated with the second season episodes "Hollywood Babylon" and " All Hell Breaks Loose", the studio wanted the series to expand. Because of this, the war was initially intended to be depicted as large-scale. Though the studio was fine with the episodes going over-budget, production on "The Magnificent Seven" went severely over-budget. The network demanded that future episodes stick to the allocated funding, forcing the writers to scale things back. ^[2]

Due to these factors, the war in the third season is mainly depicted through small groups of demons working independently, as the writers wanted to reflect terrorist cells. On this aspect, Kripke commented, "They were not necessarily organized, and there was a danger in that, that they could be everywhere. Each one has a different motive." ^[3] The inspiration for the cell of "The Magnificent Seven" stemmed from the Binsfield's Classification of Demons. The writers often use the encyclopedia for research, and a passage on the existence of demons who are paired with each sin led to the storyline of demons being the physical embodiment of the Seven Deadly Sins. ^[4]

Principal photography for the episode took place in Vancouver, British Columbia.

Manners wanted to approach the episode as "the original Western". (closer look)

Felt that scene of car crashing through bar wall, and then throwing holy water onto the demons could easily end up looking silly. Wanted to "pump it up and give it a lot of energy", had the holy water thrown into their faces to show the effect of it on demons. (closer look)

Hydraulics were used to break the devil's trap on the ceiling, and took two takes to film. Took forty-five minutes to take out ceiling and replace hydraulics after ceiling did not fully crack first time. (closer look)

Manners noted that Bobby becoming father-figure in John Winchester's absence. (closer look)

Knife sequence filmed in 120 frames per second. This allowed for the scene to be sped up or slowed down during post production. (closer look)

Lennertz, different music for each Sin. "Sloth was a slow, lumbering, creepy low-end thing. (21) Ruby's intro, quarter scraped against a cymbal to create scraping metal sound, "a little otherworldly". (21)