[3] It is Korea's first medical thriller on an infectious disease epidemic (another related film, Flu, was released the next year in 2013).

[5] Jae-hyuk is a former professor with a doctorate in biochemistry who is currently working as a pharmaceutical sales representative after losing his life savings and his job due to a bad investment he made in the stock market on the advice of his younger brother.

When a series of dead bodies are found floating in the Han River, the public is shocked to discover that the deaths are related to a fatal outbreak of virus-infected mutant parasitic horsehair worms, called Yeongasi, that can control the human brain.

Those infected show symptoms of increased hunger without appropriate weight gain and excessive thirst when the worms are mature and ready to reproduce.

The police have trouble understanding the cause of the sudden deaths, as all the victims don't show any physical symptoms but look gruesome as soon as they jump into the water.

Officials at the Ministry of Health find out that these organisms are parasitic horsehair worms that normally use insects as hosts but became mutated into a new form that allows them to infect human bodies as well.

Chaos ensues and worsens until one patient claims that he was cured by a specific type of drug called Windazole.

Meanwhile, the CEO suggests that the government buy the company in its entirety, which would then allow them to find out the drug's composition and make more of it for the rapidly increasing number of patients.

The price the CEO offers is completely unreasonable at 5 billion won and most government officials are against the idea, but the Prime Minister says there is no other option and is about to sign the contract.