I might have liked to know a bit more about the stoic policeman, but Jackaby pressed forward with the matter at hand. “So, Henderson was already dead when you arrived?”

“No, not at all. I knocked on his door to check, and he opened it, looking a bit tired and holding on to that tuning fork, but otherwise healthy. I did not wish to alarm him, so I told him I was just keeping an eye on the whole building. He bade me good night and went back inside, his lock and deadbolt clicking soundly after the door was shut. I took up a position in the hallway. I knew he was still there for several hours, because I could hear the chime of the tuning fork every minute or so on the other side of the door.

“My hearing is very good, sir, and I was watching and listening for anything strange at all in the building. It must have been close to midnight when there finally came some sort of clinking sound from the stairwell. It was terribly familiar, but I couldn’t place when I had heard it before. The hallway was dark, and I kept to the shadows as I crept over to investigate. The floorboards must have given me away as I got nearer, because when they creaked under my footstep, the noise stopped. I raced in and had a look, but there was nothing in the stairwell.

“I did not dare leave the third floor with Henderson unguarded, so I slipped back down the hallway toward my post. I could see his door clearly as I came nearer—the hallway lights are kept lit at night, and the moonlight through the window was even brighter. As I drew close, I could swear I heard a noise in his room, just a bump in the night. So, quiet as a mouse, I listened at the door. I must have listened for five or six minutes, not moving, barely breathing, but not another sound came from Henderson’s room. That was when I knew something was terribly wrong.”

“You knew something was wrong because you . . . didn’t hear anything?” Jackaby asked.