Stone was a 29-year-old stockbroker who disappeared in October of 1988. On October 28th, he was hosting a party and lost his temper with a friend, leading to an argument and fistfight. Ashamed at his behaviour, he told his family and friends that he was going on a walkabout in the desert on Halloween day, to reflect on his conduct.

Witnesses recall seeing him wandering and muttering to himself, but then he was just gone. Search parties found clues to where he wandered based on his abandoned car, dropped change, his lost watch and scribbled mathematical sequences written in the sand, but there was no trace of David.