Verse: 

I’ve got a problem that is bothering me.
I’ve got a real insoluble mystery
It would stun G. K. Chesterton – foil Conan Dyle –
Stump Humphrey Bogart and Bacall. 

Chorus: 

Who’s gonna investigate the man who investigates the man who
      Investigates me?
I don’t doubt my loyalty,
But who knows just what his might be? 

Who’ll check the record of the man who checks the record of the
       man who checks the record of mine?
Seems to me there’s gonna be an awfully long line. 

One more problem worries me – pardon my strange whim –
But who’s gonna investigate the man who investigates the man
       who investigates him? 

Interlude: 

Maybe they won’t like the clothes he’s wearing –
Maybe he has too much class.
Maybe he’s a guy who’s fond of herring,
Maybe he drinks tea from a glass.
Believe me, brother, that won’ pass. 

Back to Chorus: 

Seems to me there’s gonna be an awfully long line.
One more problem worries me – pardon my strange whim—
But who’s gonna investigate the man who investigates the man
     Who investigates him?