THE PLT RECEIVED A WX BRIEFING FOR A NIGHT, BUSINESS FLT. AT THE TIME OF THE BRIEFING A REPORTING STATION 22 NM NW OF THE ACDT SITE HAD A BROKEN CEILING AT 2300 FT WITH GOOD VIS. THE ACDT OCCURRED ABOUT 2 HRS AFTER THE BRIEFING LESS THAN 2 MI FROM THE DEPARTURE AIRPORT. AT THAT TIME THE REPORTING STATION HAD A BROKEN CEILING AT 1000 FT. THERE WERE NO WITNESSES TO THE ACDT BUT RESIDENTS OF THE NEARBY TOWN SAID IT WAS A DARK, CLOUDY NIGHT WITH GOOD VIS. THE INVESTIGATION REVEALED THAT THE ACFT CRASHED IN A STEEP LEFT BANK, NOSE LOW ATTITUDE. EXAM OF THE WRECKAGE DID NOT REVEAL EVIDENCE OF A MECHANICAL FAILURE. THE INVESTIGATION DID REVEAL THAT THE PLT AND PASSENGER HAD WORKED A NORMAL DAY AT THEIR HEARING AID BUSINESS AND ATTENDED A CHURCH MEETING UNTIL ABOUT 2300. THEY ALSO HAD A BUSINESS MEETING SCHEDULED IN OGALLALA THE NEXT MORNING.