Karyn thought fast again and said "I wish Jon didn't want to eat us."
Both rocks glowed, then Karyn and Jane felt woozy as they began to transform into plants themselves, dropping the rocks on the floor. Karyn became a small tree and Jane became corn stalk. Jon's double looked over them and became disappointed. He didn't like eating plants. He wanted to eat human flesh. At the very least, animal flesh.
So he ignored the new plants (and the wishing rocks) and left the house to find his meal.
