One cave, where there is just a small room and a locked door, has another entrance. Louis will give you a quest after you've done a few others around the village; don't take the easy solution (mindreading) and you will eventually get that door open from the other side.
In the cave with the treasure chest, if you could go through the broken door and then right, you would hit the wall that you need to examine (from the other side).
one of the bricks is actually a pressure plate
