One piercing note

I am working on the quest, “One Piercing note”. I started chasing the killer after the final cut scene in the basement, and now am in a glitch. I come upstairs from the basement, and all NPCs disappear. If I try to leave the temple, they return. As soon as I walk on to the temple grounds, I am immediately transported back to the basement entrance, and all NPCs are gone again. All I am supposed to do is climb the tower,and talk to the killer, but when I get up there, again, no NPCs. Suggestions?