During the Republic of China, Shen Heting, the ancestor of the Shen family, and Jiang Wantang, the ancestor of the Jiang family (Jiang Tang's biological great-grandmother), were lovers. Jiang Wantang was a famous female calligrapher and painter at that time. She created a manuscript "Twin Locks", which used metaphorical pictures and words to record the truth of a "Fire in the Shen Family Library" - the fire was not an accident, but someone wanted to burn an account book that could reveal an unjust case at that time. Jiang Wantang rescued the account book from the fire, but was framed as an arsonist, and ultimately died in depression. In order to protect her, Shen Heting hid the account books and the manuscript of "Twin Locks" in the wall of the Shen family's old house, and left the key and puzzle behind.
A hundred years later, Shen Du's grandfather discovered the manuscript and key while renovating the old house, but the manuscript was broken. He vaguely realized that the fire that year was related to another relative of the Shen family. While investigating, he also died in an "accidental fire". After Shen Du took over, he found that all the clues pointed to a "Jiang Wantang Relic Box" that was about to be auctioned, and the key to that box happened to be the bronze key in Jiang Tang's hand.
