Pilots Tae-in and Gyu-sik are set to fly to Gimpo. Under the guidance of flight attendant Ok-soon, passengers are busy boarding. However, shortly after takeoff, a homemade bomb explodes, turning the cabin into chaos.

Three friends, whose lives have been drifting apart, reunite for the funeral of a fourth childhood friend. When looking through their childhood belongings, they discover a trunk which contained details on a quest their friend was attempting. It revealed that he was hot on the trail of the $200,000 that went missing with airplane hijacker D.B. Cooper in 1971. They decide to continue his journey, but do not understand the dangers they will soon encounter.