Warning: The spoilers in this question may spoil the game plot for you.
Okay, so near the end of the game you find the key to the cave. It's attached to a backpack, which is tied to a tree,
which has an alarm that goes off when you find it.
I don't really understand why I found it. I mean, I know that
I used my signal tracker thing to find it, and presumably it was the alarm that set my tracker off, but Ned Goodwin spends the whole game trying to keep you from finding the cave. It is totally unclear to me why, right at the end, he apparently abandoned that plan and set you up to find the key, and thus Brian's body. This goes against everything he spent most of the game doing and when I later found his camp, I didn't find anything that explained his change of heart. In fact, I found a note about how he lost the key.
How did the key get there?