I think morality can exist without a good in the context of a group of people coming together and agreeing on what they want the rules of their society to be. I don't think this explains our conscience however, and the only accountability is from fellow human beings, which essentially means that what you can do without being caught is not bad. An act is only wrong if it breaks a predecided rule and you get caught. If you can get away with it, it isn't wrong. The problem is, multiple societies have decided that similar things are right or wrong, which seems awfully coincidental if there is not some larger overseer like a god. Another thing is that much that we consider right or wrong does not fit in with the laws, and yet still seems good or bad. It seems good to gain wisdom, yet no one got together and agreed that this was good. It is good to be courageous, yet this certainly is not impelled by law. But all agree that courage is a virtue, and people feel bad when they act cowardly even though there is no law against cowardness. So I think the outward laws that come out of morality could, without a law be agreed upon and developed; but I think there are many virtues that could not have come about without some being greater than humankind instilling such things in us.
Blessings,
-Brandon