C55 Hidden secret

Chen Keke brought me to the first floor from the third floor. Looking at the quiet hall, she gave a brief sensing of the situation before walking to the stairs on the left side of the pub. When we reached the stairs, Chen Keke lightly patted on the partition and said to me: "Gu Chen, is it here?" After saying that, Chen Keke patted on the staircase partition. After confirming a position