I volunteered to help a friend with an electrical problem she was having - two of the receptacles in her bedroom did not work. All the receptacles that I looked at had two black wires and two white wires, which I interpret as they are all in the middle of a run. The wires in all the receptacles used the "push-in" connections rather than screw-down connections, and some had come loose. I replaced one of the receptacles as the push-in connectors didn't seem to grab any more. At this point, the receptacles still didn't work. Next I went to a working receptacle in the bedroom and found the same problem, with evidence of arcing on one of the black wires. I replaced this receptacle and, Ta-Dah!, all receptacles in the bedroom worked.
Now comes the problem. There is also a switch on the wall that always appeared to do nothing. I was assuming that the switch controlled one/both of the non-working receptacles, but after my fix all the receptacles worked while the switch was in the off position. Plus, when the door is opened, the switch is behind the door; if it was intended to turn on a room light (there is no ceiling fixture), then it should probably be on the other side of the door. Finally, when I turn the switch on, the circuit breaker trips. This is the same circuit breaker that controls the outlets in the room. The light switch is single-pole, and appears to be the end of a switch loop - the black wire goes to one side of the switch, and the white wire goes to the other side of the switch. The only other wire in that box is the ground, which is attached to the box itself.
Maybe there used to be a light fixture, and it was wire-nutted together and plastered over? How can I trace the wires through the walls? I suppose I could simply disconnect and wire-nut (separately) the offending wires in the light switch, but I'd like to get it all set up correctly.