Wow, I'm confused right now. The way he leapt up and moved back and forth seemed almost like there was something happening within him. Instead of a Kryptonite cage, could Luthor have planted a tracer or some form of chemical or...something...on him and warned him to stay away from Lois? That wasn't natural, and it wasn't like Clark at all! Plus, there's something more than just reticence keeping him from telling her the whole truth.
I'm a little frustrated with Lois at this point because before the revelation, she really should have been latching onto his phrases and the way he keeps saying that he CAN'T tell her. After the revelation, I can understand her being mad, but on the other hand, after whatever just happened, she should be a bit embarrassed about her own behavior, throwing herself at first Superman and then Clark. And, knowing both of them as she does, why doesn't she realize that something nefarious is going on?
Also, she ran out right when he was prepared to tell her what was going on!!! And she's furious at him for 'torturing' her when obviously she's causing just as much pain for him, so it seems kind of one-sided at this moment.
I don't know how all this will connect together, but I know that something more than what we're seeing is happening. And I'm not so sure that Lois knowing Clark is Superman is going to help right now; it almost seems like it will hinder solving whatever problem is driving the plot.
