There was a fire.

Pilots think it's electrical in nature, so they turn off the master breaker switch. The plan was to turn things back on to isolate the source.

First thing I'd turn on beside basic nav and cockpit controls would be the autopilot, so I could get out of my seat and go see if I could find and put out the fire.

Too late. The crew probably ends up doing a few things to try to save the plane (course correction, altitude change, etc) but are eventually overtaken by smoke, flames, or all of the above.