1x1 - Episode 1

April 30, 2021

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.

1x2 - Episode 2

May 1, 2021

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.

1x4 - Episode 4

May 8, 2021

1x5 - Episode 5

May 14, 2021

1x6 - Episode 6

May 15, 2021

1x7 - Episode 7

May 21, 2021

1x8 - Episode 8

May 22, 2021

1x9 - Episode 9

May 28, 2021

1x10 - Episode 10

May 29, 2021

1x11 - Episode 11

June 4, 2021

1x12 - Episode 12

June 5, 2021