I see both at fault, but I admit my sympathies lie with Clark.
Lois, quite simply, did not even consider Clark's feelings or his happiness when she pushed him aside and did her best to show him that her work came before he did; Clark, at least, is doing what he *believes* will be best for Lois.
Also, I don't really see Clark as stupid. Mistaken, or even simply WRONG, but not stupid. His wife cried when they made love. Given his own deep grief over their inability to have children, along with the fact that there was absolutely no other evident reason for her tears, I think it is entirely reasonable for him to make the assumptions he did. Now, his assumptions were wrong, as we know, but *if* they had been true, then I don't think he could be called "stupid" to believe a divorce might be their best option.
Anywho.... as I said before, and as others have said,
these two need to talk! Unfortunately, Martha's ill-advised (yet completely accurate) comment that Lois will never leave him, knowing he wants to be with her no matter what, pretty much nipped in the bud any hopes I had of that happening any time soon.
I cannot wait to see what happens next. When do we get Part 6?
