Source: ACBL Bulletins
Bidding commentary: West has a normal passed-hand takeout double: 9-11 high-card points with shortness in opener’s suit. South’s hand loses a little of its luster after the double because the 
Q and 
K may not be as good as they look. As it happens, the Q is working but the K may be in jeopardy.
Play commentary: For South, there is good news and bad news. The good news is that dummy’s 
A is facing your singleton, so nothing is wasted there. More good news is that the North’s spades will surely afford a diamond discard for declarer. The bad news is the diamond situation. If East can get in early to lead a diamond through your king, you could lose three diamond tricks. Consider East the danger hand.
Further play commentary: The only way East can get in to lead a diamond is with a trump. For example, if you play the 
A and the K and East winds up with a winning heart, you are probably going down. When you try to pitch a diamond on a spade, East ruffs the third spade and fires the J through your king. Curtains for you.
The answer is to try to make sure that East doesn’t get in with a heart. At trick two, lead a low heart from dummy. If East plays the 8, insert the 9. West wins, but cannot put East in for a diamond play and you emerge with 10 tricks: five hearts, four spades and the A. Had East played a heart honor at trick two, win the king (noting the fall of West’s queen), lead a low spade to the jack (or the queen to the king) and lead a second heart. If East plays the 8, insert the 9. If East plays a second honor, win the ace and hope hearts are 2-2. If East shows out, play the A and a heart,
giving up the lead to West and you have your 10 tricks. Declarer is in trouble if East holds Q-J-10 or Q-J-10-8, but with the latter holding East might have doubled the final contract.