Unfortunately for Jon, his younger sister Zoe had heard of the stone while grandpa was still alive and had guessed that the stone was given to Jon as his inheritance. If anyone, Jon was always grandpa's favorite.
While Jon slept, she snuck into his room, rummaged through her brother's secret spot, and finally found the wishing stone.
Zoe snuck back into her room to play with the stone before Jon woke up, not realizing that it wasn't her grandfather's stone, but actually a different one. If Zoe used it, all of her wishes would be granted to Jon (and only Jon) as if he made the wishes himself. But, of course, if he didn't hear the wishes made, he wouldn't know that anything was different.
Sitting on her bed, Jon's Goth sister said "I wish ..."
