In a tense national crisis, the life of Jae-hyuk, a former professor with a PhD in biochemistry who now works as a pharmaceutical sales representative after a devastating financial loss, spirals into a race against time. His brother Jae-pil, a detective who carries guilt over how he squandered Jae-hyuk’s savings, teams up with him as a deadly outbreak unfolds. Across Seoul and beyond, a string of mysterious deaths tied to a brutal hunger and thirst drives the story forward as the Han River becomes a haunting backdrop for a far-reaching biological nightmare: a fungus-like parasite named Yeongasi that can manipulate the human brain.
The trouble begins with the discovery of bodies washing up along rivers nationwide. Victims appear malnourished and incongruously gaunt, yet their bodies surface with no obvious external injuries—until the parasitic worms are seen, sometimes swimming near the corpses, revealing a horrifying mutation that allows these horsehair-like organisms to infect humans. As the Ministry of Health identifies the culprits, the public gaze shifts to a potential solution in the form of a drug called Windazole, rumored to cure those infected. However, the use of any anthelmintic prescription proves perilous, intensifying pain and ultimately leading to death for many who seek relief.
In the scramble to save lives, the government appeals to ChoA Pharmaceuticals, the company at the center of Windazole’s creation. Yet the tale of the medicine is tangled in corporate mismanagement since the company’s acquisition by an investment group. Officials demand transparency about the drug’s composition, but the CEO resists, citing stockholders who refuse to disclose the recipe. As the outbreak worsens—more people rush to hospitals, pharmacies overflow with desperate customers, and rivers become seemingly endless corridors of panic—the investigation digs deeper into the seed of the crisis.
A pivotal shift arrives when Jae-pil uncovers evidence pointing to the workers at ChoA who engineered the crisis as a calculated stock manipulation scheme. He tracks down a former member of the research team and forces a confession: years earlier, ChoA’s researchers studied Yeongasi to unlock the protein that could control the brain, hoping to unlock cures for diseases like Alzheimer's. They developed a mutant version using mammals as hosts, but the company’s sale scattered the team. Disaffected researchers reunite to unleash the parasite, artificially inflating demand by staging a public display of treatment, while stock is bought up and profits soar. The plan—to store thousands of doses and pressure governments into accepting windfall deals—works until a confrontation in a hidden storage facility.
When Jae-hyuk and Jae-pil finally secure access to the remaining drugs, a fatal turn occurs: the door to the storage is sealed and the building is set ablaze. The two survive, but their informant is murdered by a mysterious figure who later reveals himself to be the head of the research team in disguise, exposing the core betrayal. With the drug burned and the conspirators scattered overseas, the Prime Minister confronts an almost unstoppable temptation: a government purchase of ChoA that would reveal the drug’s recipe and allow mass production. The offer, priced at an exorbitant sum, is rejected by most officials, yet perilous pressures linger.
In the midst of the chaos, Jae-hyuk’s scientific instincts kick in. He identifies that, even without Windazole itself, a drug containing the same active ingredient could treat the infected. This realization prompts a broader collective effort: pharmaceutical companies rush to synthesize an effective remedy, leveraging chemistry to combat a crisis that had seemed almost unsalvageable. The country begins a slow transition from panic to a coordinated medical response as new treatments emerge and save countless lives.
The film closes on a personal note. Jae-hyuk and his family find a moment of respite at an amusement park, where he muses about vacationing overseas—an attempt to escape a world where Yeongasi might surface anywhere. His wife teases whether distant countries harbor the same threat, and he offers a tense, cautious smile. The moment is shattered by a sudden focus on a dead body floating in New York Harbor, a chilling reminder that the consequences of the outbreak may extend beyond national borders and that the fight against Yeongasi could be far from over.
The production features a supporting cast that lends additional texture to the story, including Anthony Craig Fairbrass and Silvia Victoria Broom in secondary roles, enriching the human dimension of a thriller built around fear, ethics, and resilience. The narrative remains grounded in its neutral, investigative tone, presenting a multilayered portrait of a society pushed to the brink by a deliberate manipulation of science and medicine, and it ultimately centers on the ingenuity of individuals who refuse to surrender to a hidden, calculated catastrophe.
