You follow the voice down a long hallway. Saving electricity is laudable, but this is extreme. You truly cannot see your hand in front of your face. You trail your fingers along the wall to stay oriented.
The voice never grows louder. Or softer. It must be some fancy whole-house PA system.
The hall dead-ends. You feel a doorknob in front of you. And one to each side. You look over your shoulder, the way you came. The only light is a small dot impossibly far away.
"Come in," repeats the voice.