JohnP: Hi. You may want to check the song I linked above and the many good links Malcolm linked there. Start, maybe, with the Bodley one at the bottom. For betrayed & destroyed read falsely promised to marry, lured to the woods then murdered & dumped in a lonely grave. Commonly she suspects her fate & pleads for her life and he explains he's been digging her grave all night & doesn't want to waste it. Often she is a little suspicious when they never arrive at his friends' & especially so when she spots the shovel.

There are a number of songs called "Pretty Polly" but I think the usual one follows the story pretty well. Without, as has been said, the ghost element. Usually.

Possibly you've mixed it up with the "House Carpenter?" I've done that. I just try to allways call it "The Deamon Lover." That helps.

:-)