Derek Cho, portrayed by Steven Yeun, is thrust into a chaotic scenario as he sheds light on the ID-7 virus, also known as the "Red Eye" virus. This virus is wreaking havoc worldwide, targeting the neural pathways to erase moral inhibitions, thus driving individuals to give in to their darkest impulses. While it lacks lethal effects, those affected may unleash a hidden potential for violence, as demonstrated in the first known case where Nevil Reed committed murder, only to escape liability due to the virus’s influence.
At Towers and Smythe Consulting, where Derek works as a lawyer, he initially embarks on his career with high hopes. However, he finds himself engaging in back-stabbing corporate tactics, scheming to clamber the corporate ladder and earn that coveted corner office. One fateful morning, Derek discovers his favorite mug has vanished and encounters an irate client, Melanie Cross, who is desperately seeking an extension on a loan but doubts Derek’s ability to assist her.
As the plot thickens, Derek uncovers that his boss, Cara, known as "The Siren" for her persuasive influence over the bosses, has sabotaged his reputation by attributing a legal mishap involving the massive company Vandacorp to him. In a meeting with his superiors, despite his protests, Cara manages to convince John Towers of Derek’s incompetence, resulting in Derek's unexpected termination. Even his friend Ewan proves powerless to aid him as a colleague, dubbed "The Reaper" [Dallas Roberts], delivers the devastating news of his firing.
To Derek's horror, he soon discovers that the office building is under quarantine due to the ID-7 virus infiltrating the ventilation system. With the CDC working to neutralize the threat, Derek realizes that, as an infected individual, he is free from accountability, prompting him to violently lash out against the security staff in a bid to confront Towers. Unfortunately, he ends up facing off against "The Bull" [André Eriksen], who mistakenly kills Ewan, further igniting Derek's rage.
Subsequently, Derek ends up trapped in an empty office alongside an equally infected Melanie. After securing a call to Vandacorp to prove his innocence, the duo forms an alliance, plotting their escape from the basement and devising a plan to exact revenge on those atop the tower responsible for their turmoil. Their path is fraught with chaos as they confront the menacing Reaper and dispatch two security guards in their quest for retribution. Ultimately, Melanie’s fiery resolve leads her to eliminate the Reaper with a power saw.
With the key card obtained, Derek and Melanie bravely storm the office of "The Siren" but face a horde of co-workers defending her. The Siren's assistant, Meg, ultimately betrays her boss, destroying the key card when she learns of a promotion, and swiftly kills The Siren with a pair of scissors. As they regroup in IT, their mission continues to evolve; they cleverly manage to manipulate their chances against Irene Smythe, who initially blocked Melanie's loan extension.
Through various strategic maneuvers, Melanie escapes from her constraints to deal with Smythe, setting the stage for an explosive showdown. In an intense final encounter, Towers tempts Derek with partnership offers in exchange for abandoning his desire for revenge. However, fueled by the events spiraling around him, Derek rejects the offer and engages in a fierce battle against Towers. The board empowers Derek to conclude the conflict, leading him to send Towers hurtling off the penthouse railing, resulting in a fatal drop just as the quarantine lifts.
In the aftermath, Derek lifts himself to a higher position within the firm—if only briefly—to address Melanie's loan extension before departing the cutthroat corporate world entirely for a new life as an artist alongside her. He leaves the audience with a powerful reminder to reclaim their lives before it spirals out of control, juxtaposed with the haunting image of Towers' body meeting the ground in a dramatic splatter.
