Earl Richard, or Young Hunting. ER visits his mistress brags about how he wont stay because he has found someone hotter, then hugs the mistress. Surprise, surprise, she stabs him.
A bird accuses her, she tries to trick it. My favourite recording is by Spiers and Boden. Here is a youtube, it starts at about 5:15 in. http://www.youtube.com/watch?v=9ILHUpi_ZKY
You can find the words here, but I would ignore the silly bit about transposition of souls.
http://www.informatik.uni-hamburg.de/~zierke/steeleye.span/songs/younghunting.html