The Riddle Stone Part1

"How do you know the answer to all these riddles, Hong?" asked Ty.
"I don't know," said Hong. "They just come to me."

Today, I read "The Riddle Stone Part 1".
It's one of the Oxford Reading Tree series, level 7.

One day, Chip's father found a stone under the floor in the house.
Some strange things were written on it. His father was going to throw it away, but Chip kept it. Next day, he went to school, and showed it to some friends.
Hong, his Chinese friends, said, "It is written in Chinese." Hong showed it his grandfather. His grandfather noticed that it was like a riddle.

Chip and his friends were took to a rocky valley in China by the magic.
What happened in their journey...?