Clean.
From the moment he steps into the motel, the first feeling Han Dong has is "clean"... this intuitive feeling is familiar to him, because he often works in a sterile laboratory.
The cleanliness of the entire motel seems to be prepared specifically for an autopsy room.
Following the likewise clean underground corridor, he comes before the tightly closed iron door (with rubber sound insulation strip) of the autopsy room at the end.
Yu Wu suddenly covers his ears with his hands... blood traces down from his ears, eyes, nose, and mouth.
Because it was too quiet beforehand, the moment the autopsy room was opened, a large amount of "interference" suddenly poured into Yu Wu's ears.
He couldn't react in time, though he managed to cover his ears promptly, his hearing was slightly damaged.
Yu Wu's ears are the key to their team's victory.
