Just before sunrise a number of gruesomely
skeletal bodies are found floating in the Han
River. The people appeared to have died in
some kind of mass drowning. Before anyone
can get to grips with the situation more and
more cases of people being found dead by
drowning surface across the nation. The cause
is soon determined to be a mutated parasite
called hairworm that brainwashes its host into
jumping in water and committing suicide. With
a short incubation period, a 100% fatality rate
and no sign of the cause or a cure, the country
descends into nationwide hysteria.

Pharmaceutical company salesman Jae-hyeok
discovers that his family has become infected
with the parasite and is desperate to find the
cure. In doing so he uncovers a frightening
conspiracy behind the infection.