On a beautiful May morning at New York's JFK Airport, a routine plane departs for San Francisco. Security agent Bernice Adams finds a postcard of the Golden Gate Bridge bearing an ambiguous message. Who left the postcard behind, which flight is that person on, and what exactly does the message mean? Her supervisor dismisses her concerns but she is compelled to contact Homeland Security. As the flight takes off each of the passengers is looking forward to reaching San Francisco, whether it's for a family reunion, a wedding, or a new way of life. But as it emerges, there's someone on the flight planning something terrible and these strangers' lives entwine as they come together to help to avert a tragedy at the eleventh hour.
