Han Sen climbed the pine tree, but still couldn't see Bao'er.
"Bao'er, where are you?" Han Sen shouted.
"Here." Bao'er's head popped out from behind a metaphysical wall the tree brushed up against.
Seeing just her head, looking at him from outside what appeared to be a stone wall, he was perplexed, to say the least. He reached over with his arm and tried to touch the same wall Bao'er's head was sticking out from, and much to his surprise, it went right through. It was an illusion.
The wall looked rock-solid, but that was only in appearance. There was nothing physical there, at all.
"Daddy, come!" Bao'er said.
Han Sen pulled his whole body through, and when he looked up, he noticed he was in a large cave. Looking back, he could see the pine tree he had climbed, and the rest of the environment. It was like a one-way mirror of sorts.