Xie Lian was hiding something.
Hua Cheng didn’t know what, but what he did know was that whatever it was required Xie Lian to be away quite often. Now, the fact that Xie Lian was hiding something did not bother Hua Cheng — selfishly, it was the separation that caused him distress. He missed Xie Lian dearly (he missed Xie Lian when Xie Lian went to the bathroom, but that was besides the point.)
Then, one day, Xie Lian grabs him and asks to be taken to the Cave of Ten Thousand Gods. Naturally, obviously, Hua Cheng takes his husband there without hesitation.
Xie Lian leads him by the hand once they get there, his grip a gentle and beautiful thing. Hua Cheng cherishes the physical contact of his beloved.
Xie Lian stops after a while, standing in front of a structure covered in a cloth. He tells Hua Cheng to stay right where he was, and with a growing sense of confusion and curiosity, Hua Cheng does exactly that.