As Casper Galloway stands sentinel over his grandfather Horus's Occult Barn, the responsibility weighs heavily on him like a suffocating shroud. The tragic loss of his father during a perilous shop demonstration has instilled in Casper an irrational dread of anything that could jeopardize his safety. When Horus is set to receive a lifetime achievement award, Casper takes the reins, striving to ensure everything remains in perfect order while his grandfather is away to collect his well-deserved honor.
Upon Horus's return, he brings not just a trophy, but also a grave warning: “No one is to come within spitting distance” of an ominous urn adorned with a skull, displayed high on a shelf. He recounts the sinister history of this cursed object, revealing that Casper's great-grandfather, Gilbert Galloway, had once imprisoned a vile spirit within it. Folklore dictates that if this spirit is unleashed, it will herald nothing but chaos and destruction for those who dared set it free.
In a twist of fate, Charlotte, the girl who has caught Casper's attention, visits the Occult Barn. To impress her, he decides to offer a complimentary item to loyal customers. However, the situation quickly spirals beyond his control as more friends join the fray. Eager to showcase his grandfather's captivating collection, Casper takes the urn down, but in a moment of clumsiness, he drops it, unleashing its dark energies into the atmosphere.
Despite Casper's urgent cautions about the emerging dangers, his friends regard him as paranoid, dismissing his fears as mere attention-seeking. They concoct a playful curse, declaring that anyone who locks eyes with them after 10 PM will succumb to a fate dubbed “zemon.” Intriguingly, the zemons transfer their curse through hickeys instead of bites, and those unfortunate enough to fall victim will meet a gruesome end before rising from their graves. As if that wasn't enough, they add a bizarre rule: granting a French kiss to a zemon will bind them as a loyal servant.
With a sense of impending dread creeping in, Casper's friends recognize that they have until dawn to break the curse or be doomed forever. But their attempts to find a straightforward solution falter, leading them to contemplate a monumental task ahead. As the witching hour nears, unease envelops Casper, who races to prepare for the doom he firmly believes is on the horizon. His mother, however, remains blissfully unaware, assuming he is simply misguided.
When 10 o'clock strikes, skepticism clouds Casper’s mind. He confides in his mother about the strange happenings at the Occult Barn, yet she dismisses his worries as the ramblings of a concerned teenager. Meanwhile, chaos erupts on the football field as players and cheerleaders alike fall victim to an unseen malevolence, illuminating the devastating reality of their earlier prank.
Casper’s own life unravels further when he finds his mother in a precarious situation, attempting a bath oblivious to the risks at hand. In the midst of this supernatural turmoil, he encounters his friend Becky, whose boyfriend has already become one of the zemons. Her realization of the curse's dreadful impact is underscored by her palpable fear as they head towards the football field, where the scene is grim—lifeless bodies surround them, leaving only Casper and a few others standing amidst the horror.
As the zemons awaken and turn their sights on Casper and his friends, they take refuge in the home of Seth, another friend from their circle. Seth reveals the curse's gruesome attributes, stating that any eye-contact with others only intensifies the deadly implications. Racing against time, they flee in Seth's reliable Winnebago, grappling with their desperate attempts to decipher the curse's mysteries.
In a shocking twist, Horus makes his presence known once more, his expression a mixture of disbelief and sorrow upon witnessing the calamity that unfolded in his absence. Before he can share the vital knowledge needed to reverse the curse, he becomes ensnared by its dark forces, with his trophy grotesquely embedded in his skull. Yet, in a fleeting moment of clarity, he instructs the group to delve deeper for the items required to imprison the malevolent spirit once more.
Driven by an unwavering resolve, the group sets out to acquire the necessary components: the ashes of the previous urn (which Casper had prudently stashed in his backpack), a human skull from their college's anthropology room, a heart harvested from a toad’s dissection, an urn (ultimately swapped for Seth's cup after Dazzle is claimed by the zemon curse), and Horus’s treasured timepiece, which they must reclaim from his grave.
As they navigate the perilous terrain, most of their friends fall victim to the zemons, leaving only Casper and Charlotte as the last standing. A revelation in ancient texts indicates that Casper's sacrifice is essential for breaking the curse. With determination, he contemplates setting off a grenade, preparing for the final farewell. Yet, fate intervenes, reversing time to just before the urn's shattering; they retain the memories of their harrowing experience, ensuring they won't unleash another curse.
In a poignant closure, Casper and Charlotte celebrate their graduation with Horus, expressing their eagerness to join his Occult Barn staff to support their future together. This news delights Horus, who decides to embark on his first vacation, hinting at the sun-kissed beaches of Hawaii. As he prepares to leave, the couple shares a passionate moment, inadvertently knocking over the urn, leading them to utter the foreboding words: “We're so dead.”
