Got a call from a customer I did an addition on their house 4 years ago. A new service was installed at that time to the home to accommodate the new circuits needed for the addition plus the old breakers were zinsco about 30 years old so we replace all the breakers and the service. He had a breaker flip during the night and reset it but lost a few plugs on the circuit. It is a 15 amp with 14/2 romax and about half way down the line a plug with power the next dead. After pulling out a few of the plugs of the circuit and seeing nothing wrong I ran the ohm meter across the ground and the neutral at the dead plug and had a closed circuit with the wires unhooked on the prior plug. So after a bit of time I cut open the wall to follow the wire in the wall. Just out of the box the wire had melted at a romax staple and burned about 4 inches up the stud, this staple had been on the wire for 30 years. The 14/2 wire in the other boxes had white jacketed romax but this one had a black jacket not that that had anything to do with it just more FYI. I pulled a new piece of 12/2 between the boxes to replace the burned wire. I am just not sure why it happened. I also replace the breaker that was a twin Murray 15 amp and checked the power draw on the stuff he had plugged in to that circuit just a couple TV sets and cable boxes drawing about 600 watts total. All I can come up with maybe the staple had thinned the wire at that point the wire had gotten hot then shorted and the breaker failed to trip ASAP but the wire has been in the wall for 30 years. The wires in all the boxes all looked good no color and also the wire at the breaker looked good but looking at the breaker on the side you can see a bit of waves in the plastic just a little bit. Not sure if maybe a lamp might have a short and when they went to bed it happened all I was told he got up in the middle of the night and the light would not come on and he went out and reset the breaker.