Two best friends set out to rescue their pal after he's accidentally dragged to hell.
At a rundown peer carnival, idealistic promoter Remy (Nick Swardson) is desperate to bring in business. He is friends with the overweight odd carnival repairman Augie (T.J. Miller) and the insolent assistant manager Curt Meyers (Rob Riggle). After Curt discovers that the bank has foreclosed the carnival, a frustrated Remy heads down to the boat of a fortune-teller named Madame Zonar (Kerri Kenney-Silver), who is in possession of a crying Devil book. Seeing an opportunity to bring in business, Remy tells his friends that people would come around to see the Devil crying and sets the book up at The Gates of Hell, the park's main ride attraction. When Curt requests a mint Remy has in his possession, Remy forces Curt to take a blood oath so he can pay Remy back with a mint only for Curt to callously admit that he doesn't have a mint. While Remy and Curt argue, Augie sees strange weather and soon, Curt is sucked into Hell itself through the ride and Remy and Augie take a car from the ride into the portal to rescue Curt.
After landing in Hell, they discover that it is full of green lost souls and aggressive demons. After being discovered, they are taken to the Devil (Bob Odenkirk) himself, who reveals to be an aggressive, if comical being, who is just coming from a meeting. He encounters the duo and while speaking with them, mentions the Greek legend Orpheus who has a reputation for bringing mortals out of Hell. He forces the duo to hide while meeting with an angel from Heaven named Barb (Susan Sarandon) who he is infatuated with. When Barb mentions that she is aware of the mortals in his domain, he tries to show them to her, but discovers that they have escaped and calls out a search for them. Remy and Augie try to use a contraption to escape, but are discovered and are about to be apprehended by demons. Just then, a ship appears and captures them and a demon. On the ship, a mysterious figure disposes of the demon. When the duo tell the figure why they're here, the figure reveals herself to be a female demon named Deema (Mila Kunis) who Augie becomes infatuated with. She agrees to take them to Curt if they take her to Orpheus They track him using the Devil's cell phone (which Remy and Augie snagged from his office).
Meanwhile, Curt meets the Devil and hits it off with him pretty swell, but when mentioned that he is being sacrificed for not living up to his blood oath, he persuades the Devil to not sacrifice him via a contract if he puts on a show to win the favor of Barb who had a fling with him while she was dating God. It was God sent the Devil to Hell for this. Remy, Augie, and Demma locate the way to Orpheus which is guarded by Deema's mother Durmessa (Jennifer Coolidge), but they manage to make it past her. Before Deema passes through, Durmessa warns her that Orpheus isn't what she expected him to be. They use a submarine to find Orpheus and eventually locate him when he finds them through a giant robot. They discover that Durmessa was right about him as Orpheus (Danny McBride) reveals to be an eccentric slacker who is retired from bringing people out of the Underworld. Remy is the only one who seems to enjoy his lifestyle. After passing 2/3 of Orpheus's ridiculous tests, he reveals to be Deema's father as he had a fling with Durmessa, but never came home. Annoyed with Orpheus, Deema leaves and Augie decides to go with her upon being fed up with Remy's selfishness. After sharing a romantic moment, the discover from the Devil's cellphone that Curt is being sacrificed at the crossroads and head out to save him.
When Remy finds out where Curt is via Orpheus's TV, he leaves to find him and uses a Purgatory boat to catch up with his friends and reconciles with them. The Devil goes back on his deal with Curt and decides to sacrifice him anyway. After the Devil retires to the bathroom after he ate Curt's contract, Remy, Augie, and Deema manage to make it past the Demons guarding Curt and reunite with him. They find themselves at the mercy of the demons and the Devil who decides to sacrifice them all. Having a change of heart, Orpheus attempts to rescue them while disguised as the leader of a demon band, but is also captured. Barb, who the Devil called and showed her the mortals, comes to Hell via a stripper's pole and she becomes attracted to Orpheus because of his song when he disguised himself. A jealous Devil tries to use a bazooka cannon full of t-shirts to kill Orpheus. When they are escaping, a t-shirt hits Barb, knocking her unconscious. While they are falling, Remy slaps Barb awake, but the group find themselves in the lower regions of hell full of living sex-offender trees. One sex-offender tree (H. Jon Benjamin) had raped Orpheus (which he mentioned multiple times earlier). Orpheus will forgive him if he rapes the Devil, which he does later on.
Remy, Augie, Curt, and Deema are caught and bounded by the trees and when Remy is eventually held down by roots, Curt, while hanging upside down from a tree, drops a mint onto Remy. Although upset at first about Curt keeping this from him, Remy is told that if he eats the mint, the blood oath will be paid. The Devil and a demon try to stop him, but Remy eats it reopening the portal that brought the mortals to hell, sending them back to the land of the living with Deema going with them. When the Devil asks them where Barb is, she eventually appears with Orpheus flying on her, telling him about they're relationship, much to his distress. On the surface, the group discovers that Remy's idea to keep the park open is actually successful as people are lining up with coins in their hands to watch the Devil cry.
6 months later, Remy uses the money to renovate the carnival with attractions that are similar to what is seen in Hell, including an attraction called the "Gates of Heaven" with Orpheus and Barb in it.
The ending credits show a lost soul in Hell and a Demon who keeps misleading him (as he does this many times in the film) with the occurrences ending with the demon saying "Welcome to Hell."
imdb:tt2141773
