Deranged

Jae-hyuk, once a biochemistry professor with a doctorate, is now a pharmaceutical sales rep after losing his savings and job in a bad stock investment advised by his younger brother, Jae-pil. He struggles to support his family while rebuilding his life.

Mysterious dead bodies begin to surface in the Han River, shocking the public and drawing the police into a growing puzzle. The initial signs hint at a link to a dangerous infection rather than a simple accident.

Authorities identify the killer as a parasitic worm, Yeongasi, that can hijack the brain. When mature, the worms trigger extreme hunger and thirst, driving victims to jump into water to release them.

As news spreads, the Ministry of Health issues a public warning and hospitals become crowded with people showing hunger and thirst symptoms. Pharmacies flood with customers seeking over-the-counter anti-parasitic drugs, though many are misled by hype and panic.

Anthelmintics bring agony instead of relief, and a single patient claims Windazole cured him, sparking a national frenzy. The drug becomes scarce as pharmacies struggle to keep up with demand.

ChoA Pharmaceuticals, under new owners, cannot meet demand due to mismanaged production equipment. The government holds public hearings demanding Windazole's chemical composition, but the CEO asserts stockholders won't disclose it without legal compulsion.

Jae-pil uncovers evidence that ChoA workers orchestrated the outbreak to inflate stock prices and stockpile a treatment. A former researcher confesses the backstory: the team discovered Yeongasi's brain-control protein and experimented with mammal hosts before the company was sold.

The two brothers locate the storage facility where the remaining drugs were kept. A mysterious arson locks them in, but they escape while a trusted informant—the researcher who helped them—is murdered. The explosive revelation confirms the plan was premeditated and tied to the CEO.

Investigators reveal the murdered researcher was the head of the original team and a close associate of the CEO. With the survivors scattering abroad, the conspirators' long game begins to crumble.

Facing disaster, the CEO proposes a government buyout to access Windazole's recipe, offering an unrealistically high price of 5 billion won. Most officials balk, but the Prime Minister is ready to sign before the truth of the scam comes to light.

In a turn of fate, Jae-hyuk realizes that by synthesizing a drug using the same active ingredient as Windazole, he can save his family even without Windazole itself. Others join the effort to develop a cure under mounting public pressure.

Pharmaceutical companies race to produce an effective treatment for Yeongasi and avert a nationwide catastrophe. The crisis spurs collaboration and rapid drug development that meets the urgent demand.

The family sits together at an amusement park as a moment of relief before uncertainty returns. They discuss a possible overseas vacation, with the father joking about finding drugstores abroad.

The film ends with a grim image—a body floating in New York Harbor—hinting that Yeongasi could spread beyond Korea. The closing shot leaves the threat unresolved and the world watching.