Indeed, it was a case of a thief crying "Stop thief," the real ghost was Gong Banlan!
Perhaps it's not quite appropriate to say so. More accurately, the real Gong Banlan had already died; she was replaced by a ghost during the exorcism ceremony.
Even without the act of banging on the wall, Gong Banlan's words held no convincing power. After all, even she, a hobbler who couldn't walk smoothly, was unharmed, while Nalan Shuo, that slick old hand, died just like that. No one would believe her easily.
Yang Xiao and Xiang Fengchen dared not even breathe too heavily, but from the ghost's behavior of knocking on the "door," it hadn't discovered their whereabouts and still thought they were hiding in the room.
Now what Yang Xiao was most worried about was someone suddenly coming next; facing the ghost would mean certain death for the newcomer and could likely cause a series of unnecessary troubles.