Mystery Case: Full Moon Night

Every full-moon night, a murder case will occur in Tianjing City, and the dead are all related to an old case fifteen years ago - on the full-moon night of mid-autumn fifteen years ago, the entire family of the former prince's mansion was massacred. No one in the family of seventy-three was spared, except for the prince's young daughter, who was only three years old at the time. The case has not yet been solved and has become a knife hanging over the court's head. Nowadays, every month in a murder case on a full moon night, a copper coin will be left on the deceased - it is the "moon pattern coin" specially minted in the prince's treasury.