Kyle Pratt, a recently widowed aircraft engineer, is on a transatlantic flight from Berlin to New York with her six-year-old daughter Julia and her husband's casket. Exhausted and grieving, Kyle awakens mid-flight to discover Julia is missing. She becomes frantic, searching the massive, double-decker airplane for any sign of her daughter. The flight crew and passengers initially help search but soon doubt Julia's existence when there is no record of her presence on the flight manifest. With increasing suspicion directed at her sanity, Kyle pleads with the skeptical Captain Rich and the air marshal, Carson, to continue the search.

Despite mounting pressure and doubt, Kyle is convinced that Julia was aboard the plane and vows to uncover the truth. She faces significant obstacles, including the crew's skepticism, the possibility of her deteriorating mental stability, and the confined yet labyrinthine environment of the aircraft itself. As tensions rise and desperation builds, Kyle navigates through these challenges with relentless determination to find her missing daughter amidst growing conspiracy theories and rising stakes.