Seek, find.

A string of outside lights along the side of the house just quit working.

Not having any idea what the cause was, I began by finding the light at the end of the buried wire, the last one on the circuit, and pulling the bulb. A continuity test showed the bulb was good. Tracing the wire back along it's path I found a 3-way junction just where it came out of a hole at the base of the wall. It was corroded and had disintegrated the conductors.

I trimmed back the wires and re-tied the junction inside a weather-proof box.

Covered it back up with pine needles. Let there be light!