Park Dong-won (Kim Sung-kyun), a common man and his family move into a house purchased after 11 years of labour. They throw a housewarming party and invite all friends. A heavy overnight downpour creates an extremely big sinkhole, and in a mere minute, it engulfs the whole house with the people inside it. Deep down the hole, Park Dong-won, his neighbor Jeong Man-soo (Cha Seung-won), and the guests have to find a way out. As the luck would have it rain again begins to pour down, filling the sinkhole with water. They must find out a solution before time runs out to survive....