Piano piece identification -- an old mystery to me!

[somnac]

Back in the days of Napster, I downloaded a random mp3 with a worthless file name (something along the lines of "05-l.mp3".  This was many hard drives ago, and I've long since lost the original file.  The piece itself, however, has always stuck with me.  My memory has faded a bit, but I've managed to reconstruct at least the beginning.  I'd love to find the source so I can learn to play the whole thing properly.  Any help would be greatly appreciated.  Many thanks in advance!

[somnac]

I can provide the entire melody if that would help anyone, but I've only managed to reconstruct the bottom end up to that point.  I've been trying to figure this out for years!