Mary Frances Gregory was 19 when she left Parry Sound, Ontario, for a vacation to Palo Alto, California. She departed on February 15, 1978, in the company of a male acquaintance. She was described as 5 feet 3 inches, about 110 pounds, with straight shoulder-length dark blonde to brown hair, hazel eyes, and correcting braces; she was near-sighted and wore contact lenses. A mole on her waist or the right side of her chest was noted as a distinguishing mark.

According to the man who last publicly reported seeing her, they drove from Ontario into New York about three days after she left and passed through New York, Pennsylvania, Ohio, Illinois, Colorado, Utah and Arizona before reaching Nevada. He said their travel together ended on February 28, 1978, when he dropped Mary at a Las Vegas bus station roughly ten days after she left home. Mary never arrived in California, her luggage has never been found, and no one in her family or circle has heard from her since.

Her disappearance is treated as involving foul play and remains an active investigation with the Ontario Provincial Police in Parry Sound. Few facts are known beyond the last person who reported seeing her and his account; what happened after she was left at the Las Vegas bus station is unknown. Did anyone in Las Vegas in February 1978 see or help Mary Frances Gregory, or does anyone have information about the man who traveled with her?