to fortuitously presenting him with a letter found in his desk in-box he would not have received until the next morning. The letter explains that a series of murders will take place on Flight 502 before it lands. Robert Davenport notifies Captain Larkin, via the airline's direct radio channel. Donaldson and his team go over the backgrounds of all the passengers to find possible suspects, which irritates Larkin for the lack of details, causing him to be terse with an equally aggravated Donaldson who is none the happier for being talked down to while nursing a painful toothache. In the air, Captain Larkin, off duty Police Officer Daniel Myerson, and flight attendant Karen White look for suspicious passengers.