I've only ever heard this song sung by Iain MacKintosh who, sadly, never recorded it. His matter-of-fact style suited the song well, I think. (Incidentally, he sang "the rattle of his change" - see here.)

I imagine that Casey has done what a certain British royal has since made acceptable: carried on with an earlier love after marrying and fathering a child (or possibly the other way round - getting another woman pregnant and marrying her, for whatever reason). He doesn't really love his wife, doesn't really know what he is toiling for, but finds his (ex-)lover's demands equally off-putting. In short, Casey finds the demands of his double life too much and gets lost, in whatever way. It is a haunting song, and certainly one giving a lot of space for speculating and creating your own story.