A Narrow Trail                                         -      N      - 
(-------------------------------------------------)     - <---(M)---> -
                                                        -      S      -

The floor of the pass is extremely smooth, almost to the point of being
slick.  Dust and debris from ages past stir gently as you walk up the pass.
You are about to walk past when you notice a peculiar looking stone on the
ground.  Upon a closer look you see another small keyhole placed in the
middle of it.  
You dodge out of the way of a large boulder that crashes down from above!