His rock-climbing skills haven't helped Yong Nam much after graduating from college, as he struggles to land a decent job. One day, while celebrating his mother's 70-year-old birthday at a convention hall, he bumps into his old crush, Eui Joo, a former fellow rock climber who rejected him when he confessed his feelings to her back in their university days. However, when suddenly a mysterious and dangerous gas engulfs the city, he puts his skills as a rock climber to good use as he and Eui Joo try to escape it.