Both sides vulnerable.  
South deals.
                              NORTH
                              S: 6 3              
                              H: Q J 8 7 4   
                              D: 10 8 7      
                              C: K J 3   
            WEST                             EAST
            S: 10 7                          S: A 4          
            H: A                             H: 10 9 6 5 2 
            D: K Q J 9 6 4 3                 D: 5 2               
            C: 8 7 5                         C: A 10 9 2    
                              SOUTH                         
                              S: K Q J 9 8 5 2
                              H: K 3        
                              D: A         
                              C: Q 6 4  
          The Bidding:
                  SOUTH    WEST    NORTH    EAST                  
                   1S       2D      Pass    Pass
                   4S      Pass     Pass    Pass
	Opening Lead: AH
     South was looking at a hand that was potentially one trick
shy of game and while much can be said for a more scientific
auction, there is little to complain about the final contract. 
West led the ace of hearts and South was thrilled to see honors
in hearts and clubs to cover his losers.  The four of hearts was
played from the dummy, East played a discouraging deuce, and
South played the king very smoothly, hoping to look like a man
with a singleton heart.
     The defensive situation did not look good.  How would you
continue as West at trick two?
     Did you lead the king of diamonds?  I would guess that card
would be the majority choice.  Let's try to look a few tricks
into the future.  Declarer wins the ace of diamonds and leads the
king of spades.  East wins the ace and has to decide what to lead
to trick four.  A heart lead may defeat the contract if West can
ruff, but it certainly looks as though West started with two
hearts and South started with the singleton king.  If that is the
case, the potential diamond trick could go away on the queen of
hearts.  It looks right to cash the ace of clubs and lead a
diamond to partners queen, but this turns out to be wrong as
declarer ruffs, draws trump and claims.
     How about a club?  Partner will win the ace and will then
have to try to figure out what is happening.  It would not be
unreasonable for him to decide that you had some diamond holding
that you could not lead from and that you had led the ace of
hearts from the holding of ace-three and switched when declarer
dropped the king.   
     When the hand was actually played, West knew that his
partner would have a problem and so led the queen of diamonds at
trick two.  In theory this denied possession of the king and led
East to make the right play after winning the ace of spades. 
Since the diamond was a sure loser, there was no reason not to
return partner's opening lead.  The result of down one goes to
prove that one good falsecard deserves another. 
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