Tonight's episode is called "This Place Is Death," and last week's preview showed Locke climbing down into a hole, one that didn't look much like the Orchid, although they could have been at a point in time where it wasn't built yet.
My question is whether Locke is finally going to explore the cavern of tunnels that likely runs underneath the Island, possibly as an alternative way to get to the Orchid? We know from the Blast Door Map that there appears to be an underground tunnel system, possibly used by Smokey to travel around the Island unseen. Also from the Map (and confirmed by the Lost Puzzle Clues), we know that Smokey pops up around the Island through Cerberus Vents (labeled CVI, CVII, etc... on the map). This is why Smokey seemed to disappear underground after encountering Eko and Charlie back in "The 23rd Psalm" and likely where it tried to drag Locke when it snagged his leg in "Exodus." But this is one thing that has never really been investigated on the show.
So given the title of tonight's episode and that we know from the preview Locke's heading underground, I'm hoping for some Hot Smoke Monster Action tonight. After all, what could be more like death than traveling though Smokey's Supertrain transit system? :)
Enjoy the show! Review should be up tomorrow morning, evening at the latest!