The Left Hand.

SETTING:  THE OVAL OFFICE, NIGHT TIME.  A GENTLEMAN IN A CHAIR IN SHADOW.  DRESSED IN A MILITARY UNIFORM.

THE LEFT HAND:  (CALM) Hello, Mr. President.
MR PRESIDENT:  (STARTLED) Who are you?  How did you even get in here?  (MOVING TOWARDS A PARTICULAR SPOT ON HIS DESK)
THE LEFT HAND:  Don't bother, the alarm has been disabled for this meeting.  My name doesn't matter.  No one knows it, but I do work for you.  I'm your left hand...
MR. PRESIDENT:  (SITTING IN HIS CHAIR, HAS GIVEN UP ON PRESSING AN UNSEEN BUTTON) Left hand?  Which means?
THE LEFT HAND:  Little joke from before our time, your right hand is your helper that the public can know about.  I'm the helper that the public had better not ever knowing about.  We started with JFK, he was a bad boy in ways that the public still doesn't know about, we had to clean up that mess.  The conspiracy crazies are correct, he was killed by a conspiracy in the highest levels of our government; oddly enough, Johnson wasn't involved at all until he had my original predecessor tasked with uncovering the conspiracy.  Johnson thought that the truth would hurt the US too much so he had us created.  If something is just too terrible for normal channels you can contact us.  We will do things that the public doesn't need to know about, kind of like that saying about sausages and laws.
MR. PRESIDENT:  (NODDING, FAR OFF LOOK IN HIS EYES) Could be useful, if used sparingly.
 How do I contact you?  And your name?
THE LEFT HAND:  I've watched you for awhile, your "trigger" is simple.  If you need to contact me just wait until you have a meal and wipe your mouth with a napkin that's in your left hand.  It was different for your predecessor and it will be different for whoever replaces you.  Don't worry about the name, it's for our safety if you can't track me down.
MR. PRESIDENT:  (CONFUSED/QUESTIONING) "Our" safety?
THE LEFT HAND:  (GETTING UP AND PREPARING TO LEAVE) Three people know of "The Left Hand".  You, me and my second, if anything happens to me then he will take over.  (AT THE DOOR AND OVER HIS SHOULDER)  Something I need to clarify, if you do anything that can harm the US then YOU are my target.  Legend has it that Johnson himself told the original Left Hand to kill him if he did something as bad as JFK.  Please think about that before you contact the governor you were planning on meeting with tomorrow.

My latest stab at dialogue from a play/film perspective.