Cai Shu stopped abruptly at this point. If this Poisonous Gu isn't Feng Qing's doing, then it's Han Concubine's handiwork.
Cai Shu's mind seemed to clear up suddenly, as if enlightened. She thought of how she was inexplicably pressured by her family to marry, and it was to be wed to a forty-year-old widower. Then she recalled hearing what Han Concubine's maid had said, and how she had paid someone to steal the Unity Gu, surprisingly smoothly.
The more Cai Shu thought about it, the clearer it became. She was almost certain that this whole affair from start to finish was Han Concubine using her hands to plot against the Prince; Han Concubine wanted the Prince dead.
Cai Shu was shocked by this realization and also understood why Han Concubine would wish for the Prince to die.
