His mother's fantasy was that she be able to live her life over again starting from teenage, knowing the mistakes she made so that she could try avoiding making them again.
Many years ago, Jon's mother woke up. She was in a room that seemed unfamiliar to her, but which she soon recognized as her own room, when she was a teen. She got up and looked around for a calendar, which showed that she was in the middle of her second year of high school and had just turned 16.
It was like some kind of movie, she thought. The world had gotten weird on her, and she was back in the past. But she still remembered being herself.
The things she would do differently would affect Jon and Karyn's present, of course, but at this point, neither of them had been born--she hadn't even met their father. She was back living with her mom and her dad. Everything was as she had remembered it. She even caught a glimpse of her father (Jon's grandfather) holding that same strange rock he always carried around for some reason....