An undercover cop has his loyalties tested when the boss of the corporate gang he’s spent years infiltrating dies.

Jae-hyuk is a pharmaceutical worker for a medical supplies company. When a series of dead bodies are found floating in the Han River. The public is shocked to discovered 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 shows symptoms of hunger and thirst, hence jumps into the river to combat dehydration. Whilst the authorities work to find a cure, Jae-hyuk struggles to save his family when they also exhibits similar symptoms.

In the 11th year of Kwang Hae-gun, Jo-seon soldiers go to war with China after an invasion. In the middle of Manchu, three people who have barely survived are being cornered by the Chinese forces, and begin a bloody battle not with their enemies but with their friends.