Questioning the Sword

During the Wanli period, the capital city. A policeman walked out of the snow with a knife on his back. His name is Shen Yan. The father is Shen Shikai. In the twelfth year of Wanli, the entire Shen family was wiped out, but he survived. Ten years later, he returned to the capital. There was only one thing he had to do - find out whose hand held that knife. The disputes between Caobang, Si Lijian, Dongchang, and the Crown Prince... Every line leads to the deepest part of the capital, and every line is connected to the same name. The knife is still on his waist. He asked for many years, and finally someone dared to answer.