In a trouble call, owner of two story house said lost power to half of second floor. Owner after some time did mention that son smelled something few days before. No tripped breaker though in panel when arrived. Turns out, this switch that turns an exterior patio light on, hidden in closet area, was a fault. The insulation had completely melted off and hot wire burned and made contact with neutral. No equipment ground in circuit. Blanked out outlet and insulated wires with 33M electrical tape.