Often in the Pilot of a series, the writers establish characters and their relationships to others and will mention how a friend or loved one mysteriously disappeared without a trace. Because of the Law of Conservation of Detail, this becomes a form of Foreshadowing that works better than an Ass Pull when the writers run out of ideas; they can then return the relative, often through some form of Applied Phlebotinum, or else He's Just Hiding. The characters will almost Never Say "Die" when it concerns their lost loved ones; they're simply Missing-In-Action due to the "mysterious circumstances" that took them away.