From memory, Garry, the butterfly reveals the route back into the cave... so you can retrieve that other item. I imagine you've got to around about the end of what was there when I tried it. You're meant to burn down the tower... the idea, I believe, is that in the full game you'll be able to swim back there.
Oh... and French crows go Crôa Crôa apparently! :) I can't find what noise French ravens make.