At first glance, the other side of the tunnel was exactly the same as the side I entered. And I mean exactly the same: on the same side of the tree. I pulled out my compass to check, and found the second strange thing. My compass didn't point in any particular direction. The needle just wobbled around all over the place.

You might think that the woods would look out of the ordinary. Maybe it'd be inhabited by some geometric parody of trees or a surrealist coatrack or something, but it looked quite normal, for trees. Looked exactly like the woods around the fallen tree on the other side. If it wasn't for the compass, I would have thought that somehow got turned around in the tunnel. But there was something else that was different: the plastic bag with the note in it was missing. The evidence wasn't conclusive, but there was every possibility that I was somewhere else.

I started thinking of ways that I could test it. How can you tell if your world has been replaced with one that is almost exactly identical? Look for the differences, differences you can't explain any other way. Some one might have come along and removed the bag, for starters.

Not that there's weren't any other differences. It was much dimmer here, and completely overcast. I guess the weather could have changed really rapidly, but could fog really have rolled in that fast? It wasn't an ordinary fog, either, it almost wasn't fog at all, just a dimness that kept just out of reach.

I took out my notebook and started to take notes on the immediate area. It would be important to be able to document any differences, rather than trying to rely on my memory. Though, as it turned out, it didn't matter, because there was an obvious difference just a few steps away.