In the dreary confines of their office, Evan Sanders (the acting sales manager) confides in his relaxed colleague Tim about an upcoming presentation that could be pivotal for securing the lucrative Phallucite account. The atmosphere is thick with tension, intensified by an awkward exchange Evan had with Amanda, the HR head. The peculiar incident, which involved Amanda whispering sweet nothings into Evan's ear, only to be met with an awkwardly firm "no," becomes fodder for Tim, who amusingly recounts the moment to Andrew and Mike in the break room. The ripple effect of this uncomfortable encounter is soon made worse when Ted Plunkett, the branch president, bypasses Evan for a promotion, choosing instead Max Phillips (an old college mate of Evan's) as the new sales manager. Compounding Evan's distress is the fact that Max has already begun to show interest in Amanda.
As the office descends into its nightly rhythm, Mike isolates himself in a bathroom stall, indulging in some late-night gaming. Unfortunately, his pleasure is cut short when he appears to have met a tragic fate – or so it seems, as Evan discovers Mike's lifeless body only to find it mysteriously vanished by morning. Meanwhile, Max clandestinely influences office worker Dave, turning him into a ravenous vampire filled with a hunger for revenge and a demand for the repayment of sports betting debts.
With his anxiety mounting over the nearing Phallucite presentation, Evan seeks the assistance of Zabeth, who secretly pines for him. Her mission: to retrieve essential files from the ominous office basement. Sadly, this assignment puts her in grave danger, and she becomes ensnared by Max's malevolent schemes, falling victim to his vampiric curse.
Desperate to stay productive, Evan persuades Andrew to join him for a late-night work session, only for Andrew to encounter new threats when he ventures into the basement, where he’s attacked by Zabeth’s newly transformed fangs. Meanwhile, Evan rummages through Max's files, stumbling upon unsettling photos of Amanda and employee records marked with sinister symbols emphasizing danger.
As the evening progresses, Evan finds a hiding spot in a supply closet, reeling from the harrowing realization that Max is orchestrating these brutal murders. A fraught phone call to Amanda ends in calamity when Max hijacks the line, taunting Evan, pushing him closer to breaking point and exhaustion.
The following morning brings unsettling developments as Ted, Tim, and Max stumble upon Evan sleeping at his desk, unaware of the chaos brewing. Andrew emerges from the depths of the office basement, now transformed and carrying the presentation. Ted reprimands Evan for failing to handle the project, only for Max to unexpectedly champion Evan's position, provoking uneasiness amongst the remaining staff.
As Evan's warnings about a vampiric takeover begin to gain traction, he and Tim embark on a frantic investigation, with Tim sharing his own alarming observations of Max turning Elaine, their administrative assistant, into one of the undead. Despite their growing evidence, Amanda remains unconvinced, dismissing the supernatural claims of her colleagues.
Turning to security guard Frank for help, Evan and Tim discover his car has been vandalized, leaving them defenseless against the escalating vampire threat. Just as hope seems lost, the Janitor springs into action, revealing his true nature before launching a brutal attack on Frank. In a stunning retaliation, Frank impales the Janitor, eliminating the newest addition to this nightmare.
After regrouping, Evan, Tim, and Frank are horrified to learn that their co-workers have all morphed into productive vampires. Armed with a makeshift arsenal of office supplies, they prepare for their showdown with Ted, Max, and Andrew, who now pose a fearsome challenge. Ted's revelation of having sanctioned Max's vampiric activities for enhanced productivity only fuels Evan and his allies' determination.
As they confront the sinister reality, Max's intentions to eliminate Ted come to light when he coldly snaps Ted's neck. In their frantic escape, the group strives to rescue Amanda, yet they are encircled by a horde of their transformed colleagues. A fierce struggle unfolds, leading to the defeat of many of the undead, but just as victory seems in reach, Max unleashes the legal team, now thoroughly vampiric, to bolster the malevolent forces against them.
Amidst the chaos, Max forces Amanda back into Ted's office, leaving Evan, Tim, and Frank to face an increasingly perilous challenge. While Andrew takes it upon himself to eliminate Dave, tensions rise between him and Tim over the best way to handle the situation.
In the end, Frank falls victim to the relentless assault from the undead attorneys, while Evan returns to Ted's office to confront Max alongside Amanda. As the scene settles amidst the carnage, the three emerge from their chaotic battle as dawn breaks, leaving a path of destruction behind. Unbeknownst to them, Andrew is still at large, now fully embracing his vampiric powers, preparing to claim his next victim: the unsuspecting cleaning woman, whose cries will echo through the eerily quiet office as day transitions back into night.
