OK, not a Night Gallery episode. I knew about the N.G. episode   
   titled "Brenda", in which a young girl finds a shaggy monster in a pit   
   and befriends it. Later when it got out of the pit, the men forced it   
   back in and covered it with rocks. The girl comes back years later and   
   talks to the monster in the stones.   
        But I thought I remembered a similar one about a boy who found a   
   deep hole that had growling sounds coming from it, that I thought might   
   have been the one you meant. Evidently there wasn't an episode of Night   
   Gallery or Ghost Story/Circle of Fear like that though. It must have   
   been from some other series from around that time.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)