Dark Hole

After losing her husband to serial killer Lee Soo Yeon, police detective Lee Hwa Sun makes her way to Muji city in order to bring the murderer in. But unlike what she is hoping to find, she runs into an enormous sinkhole in the middle of the mountains. Black smoke arises from this mysterious sinkhole and the people of Muji are left clueless about what it is. 

The news of the sinkhole spreads throughout Muji and more people come to look. However, things go wrong as they get infected by the black smoke and start attacking each other. Not knowing how it is triggered, but a large amount of smoke ascends from the hole and slowly covers Muji city. Hwa Sun and Tae Han go separate ways for their own objectives, but they both fight their way through the chaos. 

The young girl goes missing, and Hwa Sun searches everywhere for her. When she finds her, she realizes she is within a religious cult that won't let go. Meanwhile, Tae Han makes his way to Muji Hospital with another survivor, and Mujin High School locks their doors to anyone outside. 

Hwa Sun and Do Yoon make it to the safety of Muji High School. However, they get confronted by Mr. Choi, who thinks they are a threat to everyone inside the school. At Muji Hospital, Tae Han attempts to rescue survivors on the fourth floor with Officer Park and Officer Cho. Meanwhile, Hwa Sun has a dream, telling her of another mysterious being with the black smoke.

Tae Han and the officers continue to look for the survivors in Muji Hospital. However, they get a strange feeling something is following them. Meanwhile, at the school, Hwa Sun and a few risk their lives to fetch medicine from the nurse's office. But one of them abandons them to save his own life, leaving Hwa Sun against the mutants all on her own. 

Do Yoon and the survivors at the school wait for Hwa Sun to return, but they soon find out Jin Seok had his way. Under the influence of the monster, Jin Seok takes down the barricade to the school, allowing the mutants to enter. Meanwhile, a pregnant woman desperately bangs on the doors of Muji Hospital. 

Hwa Sun and the rest escape from Muji High School, while the shaman controls the people in the hospital. As Hwa Sun makes her way to the Muji Hospital, the monster within the smoke takes control of people one by one, leaving only some to carry on. Meanwhile, Tae Han seeks refuge at a supermarket but runs into a nurse in distress.