Idealist Remy is on a relentless quest to breathe new life into the struggling pier carnival where he and his childhood companions, the quirky and portly repairman Augie, and their indifferent assistant manager Curt Myers, work. With the business dwindling and the looming threat of foreclosure from the bank, Remy seeks the insight of a mystical fortune-teller named Madame Zonar. She hands him a mysterious tome featuring a page that depicts the Devil's anguished tears. Convinced that this seemingly cursed artifact harbors the key to their salvation, Remy decides to display it at The Gates of Hell attraction.
Tensions escalate as Curt asks Remy for a rare mint, but Remy demands a blood oath as collateral. When Curt unapologetically reveals he doesn't have the mint, Remy’s anger boils over, which prompts Augie to witness a foreboding omen of doom. Suddenly, Curt is sucked into a portal inside the ride, forcing Remy and Augie to commandeer a vehicle from the attraction and plunge into the swirling abyss after him.
Their bizarre adventure leads them directly to Hell, where they are confronted by demons and ultimately brought before the Devil himself. As he ponders their torturous fate, he mentions the legendary Orpheus, famed for his remarkable ability to rescue souls from the underworld. The Devil's scheme is interrupted when an angelic figure, Barb, arrives. In a desperate bid to win her over, he plans to use Remy and Augie as sacrifices. However, they cleverly manage to escape capture with assistance from a mysterious female demon named Deema, who seems to have taken a liking to Augie.
Meanwhile, Curt finds himself in the clutches of the Devil and surprisingly forms a connection with his host, until he learns of his horrifying fate as part of a ritualistic sacrifice. In a twist, he proposes an alternative that involves putting on a show to win Barb's favor and take his place as the offering. As they traverse the labyrinth toward Orpheus, Remy, Augie, and Deema encounter Durmessa, Deema's imposing mother, who warns them that Orpheus is not the savior they hope for. Undeterred, they commandeer a submarine to breach the defenses and finally meet Orpheus, who turns out to be a laid-back slacker indulging in romantic escapades rather than fulfilling his heroic duties. Deema, infuriated by Orpheus's indifference, leaves with Augie, abandoning Remy to his self-serving ways. Amidst the chaotic scenes involving Charon’s ferry, a budding romance flares up between Deema and Augie, but they soon learn via the Devil's cellphone that Curt is in grave danger of being sacrificed at the crossroads, leading them to rush to save him.
As Remy discovers Curt's location through Orpheus's television, he sets off on a mission to reunite with his friends and repair their fractured bonds while aboard a boat bound for Purgatory. With no backup plan in sight, the Devil retracts his promise to Curt, preparing to execute his sacrifice. In a brief moment of clarity, Remy, Augie, and Deema manage to evade the demonic guards and reunite with Curt, only to find themselves ensnared by the sinister forces and the Devil, who intends to sacrifice all of them.
When Orpheus, attempting to rescue his friends by masquerading as the leader of a demon band, is captured, the plot thickens. However, he captures Barb's attention with his soulful performance, prompting her descent into Hell through a stripper’s pole, where she becomes enamored with him. Consumed by jealousy, the Devil launches a bazooka cannon filled with T-shirts at Orpheus, unwittingly knocking Barb out as she tries to help the group. Though they manage to survive the tumultuous fall, they find themselves trapped in the depths of Hell, surrounded by twisted trees representing tormenting memories, including one that had tormented Orpheus in his childhood. Touched by the tree's sincere apology, Orpheus agrees to forgive it on one condition: that it take revenge on the Devil instead.
As Remy, Augie, Curt, and Deema become entangled in the branches of these sinister trees, a pivotal moment occurs when Curt, suspended upside down like a grotesque puppet, discreetly drops a mint onto Remy's face. Initially shocked by this covert act, Remy discovers that consuming the mint would fulfill the blood oath, allowing their souls to escape the infernal grasp and return to the mortal realm along with Deema. Despite the Devil and his minions’ attempts to thwart their escape, Remy’s unyielding determination and the group's collective strength ultimately overcome the challenges they face.
Upon their return to the living world, the group is elated to find that Remy’s efforts to save the park were not in vain. Flash forward six months, they revisit the now transformed park, enriched with attractions inspired by their astounding experiences in Hell. Among these is the "Gates of Heaven" exhibit, showcasing Orpheus and Barb as central figures.
As the credits roll, a darkly comic morality play unfolds, featuring a lost soul condemned to wander the underworld who attempts to place an order at Pizza Hut, only to be endlessly misdirected by a gleeful demon reveling in his victim’s eternal suffering with the haunting line: > "Welcome to Hell." This eerie jest serves as a chilling reminder of the group's own narrow escape from the clutches of damnation.
