I Was Being Followed But By What?

I exhaled slowly.  I was trying to slow down my heart rate but fear had its grip on me. 

“Breathe.....”  

“Breathe...”  I kept telling myself.  “Slowly......breathe.”

It seemed to work and I tried to keep my thoughts focused on where I was headed and not be concerned about what was following me.  Or was I just imaging it?  The noise was a definite crackling sound, like footsteps breaking branches.  I couldn't turn around.  I had to keep going forward.