Peder summed it up pretty well: This story looks awesome. I can't wait to play it. I don't normally download demos, but I will on this one. The whole "two stupid guys by accident gets involved in something bigger than they could have foreseen" plotline is well-used, but when used right it can be good, and the whole idea of the two dimensions tied together by light is an excellent idea which I'm really looking forward to seeing done.
A few thoughts about things you might improve:
You've probably already thought about it, but make sure your two characters aren't too identical personality-wise. Of course they have some similarities as they are brothers, but make sure they're two distinct persons and not just two clones of the same person talking to each other. Give them individual wishes and needs, and individual ways of thinking. I was confused in your intro when one of the guys encourages the other to empty the guy's pockets, and when finding the amulet he suddenly changes completely his point to "it would be wrong of us to take it". It feels somehow as if his personality changed more than it should have done in those seconds. Strong personalities is the key to great fiction.
I loved the beginning with the professor walking through the ally, and especially the whole "newspapers blowing in the wind" thing. Kudos for awesome plot revelations with the perfect amount of vagueness!
The Eric-and-Chris-walking scene seemed odd, because it looked as if they weren't moving at all. Since the palm tree stood still, it seemed as if they did as well. If you made the palm pass by them in the background or something, it would look more realistic.
And forgive me for asking, but ... *why* the nine-verb GUI? Most games really don't need it, and for some reason it doesn't FEEL like the right interface for a huge dimension-spanning fantasy/sci-fi-plotline. I really think you would be better off with something more... intuitive. But maybe it's too early to say -- there are people who manage pull off the nine-verb GUI, and maybe you're one of them.