Suddenly the man was behind me, and his too-cold hand was clamped on the back of my neck.  "If you will not believe that I am what I say, then believe the evidence of your eyes," he said softly, "I could have snapped your neck before you knew I moved.  before you could draw and fire, I could kill your entire family as they sleep.  But I have no desire to harm you and yours - provided you follow my exact instructions."