Zhang Heng brought the hotel staff, a waitress on the ninth floor away, not wanting 0 to know what happened in Room 936. He didn't mind having a guide to lead the way, especially in areas he was unsure was safe. He could always ask the staff to check whether the path was dangerous. Of course, doing so would put her in danger, but it was highly unlikely that anyone from either side would harm her.
That being said, it couldn't hide the fact that Zhang Heng was using the waitress as a guinea pig. The waitress didn't realize that, of course, but she soon noticed Zhang Heng pausing between steps, crouching in front of a wall, or suddenly laying down on the ground, and his actions piqued her curiosity.
After a while, she couldn't hold back, asking, "Mr. Officer, are you investigating this matter alone?"
"Hmm… What? Why ask?"
"Nothing. It's just that usually, at least two officers will investigate the same case..."