The story begins at Dubai airport where flight Kingdom 29 is ready for a seven-hour journey to Heathrow in London. Passenger Sam Nelson boards with only a small bag, containing a gift for his ex-wife Marsha. In London, Marsha is with her boyfriend Daniel and tells Sam not to fly. Sam refuses, and on the flight, a bullet shell is found. Passengers Terry and Stewart discuss a disrupted plan, while Sam watches their suspicious behavior. Terry lies to passengers about the bullet's origin, but their doubts persist, leading them to seek clarification from the crew. Terry realizes they must act fast.