South Korean soldier Cheon Woo (Go Kyung-pyo), who is about to be discharged from the army, accidentally picked up a first-prize lottery ticket that was flying towards him near the tense military line between North and South Korea one day. However, he accidentally let the lottery ticket fly towards North Korea, which he could not get into. In order to realize his dream of being discharged from the army with the 5.7 billion bonus, he tried his best to find the lottery ticket, but he did not expect that it would be picked up by North Korean soldier Young-ho (Lee Yi-kyung). Cheon Woo, who had just missed the lottery ticket, and Young-ho, who was just a piece of paper in North Korea and had to go to South Korea to exchange the lottery ticket for the bonus, plus unexpected members joined in. In order to hold on to the huge 5.7 billion bonus, both sides decided to "cross the line" and start thrilling secret negotiations...