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

You carefully walk down the narrow path.  The ground is extremely smooth,
almost slippery.  Small pebbles and rocks are strewn about, and you take
caution not to accidentally send one flying, as it could cause a landslide. 
The walls of the cliff look very unstable, and you hold your breath, afraid
that the slightest noise or movement could spell your doom.