This deal comes from the Reisinger Board-a-Match teams at the 2012 NABC. South held:

AJ10
KJ5
K2
A10976
.

With both sides vulnerable, his partner dealt and passed. RHO opened 3. Now what?

There are two sensible calls. One is 3NT and the other is double. I don't like the diamond stopper for 3NT (because you can't hold up). If I held Kxx or even Ax, I'd be more tempted. On the other hand, I'd prefer to have one, if not both four-card majors for a takeout double. I can see arguments either way, so let's go with a double (which is what was chosen by Alan Sontag at the table). LHO passes and partner bids 4.  Ugh. Do you bid your long club suit (5)? Or, choose a 3-card major, and if so, which one?

Right or wrong, Sontag chose to pick his better major, spades and wound up in 4 on this layout:

Q872 AQ42 4 8542

AJ10 KJ5 K2 A10976

You can see that a 3NT overcall would not have worked well. Partner would (should) pass and you'd have no chance after a diamond lead. As to 5, that requires 2-2 clubs and the spade finesse. Partner's 4 was on the ambitious side. In fact, at the other table, the player with that hand faced the same start and chose to go low with 3 and played it there (making). So, a full board rests on whether or not you can make 4. 

Against 4, West leads a diamond to East's ace and back comes the K. Your thoughts?

With East holding some high diamonds and the K, you can be sure the K is offside. That means you need 2-2 clubs. Let's say you win the A, West playing an honor and continue clubs, pleased to see that West started with QJ doubleton. Next comes another diamond. Your plan?

You discard (let's say a club) from dummy and win the K. You know the K is wrong, so it is pointless to cross to dummy for a spade finesse. It would be nice if spades are 3-3. If spades are 5-1 you have no real chance. Say you lay down the A and play another spade. That would be a big mistake. If spades are 4-2 (which is with the odds, especially with East's preempt), you'd be dead. West would hold up his K to leave:

Q8 AQ42 -- 8

10 KJ5 -- 976

You can't deal with West's 4th trump. If you play another spade, he wins the king and taps dummy with a diamond, establishing his long trump. If you do anything else, West ruffs in with his small trump. So, how can you handle a 4-2 spade break?

You have to hope that the 4-2 break includes a doubleton-nine with RHO. Then, you have a chance. Just don't prematurely release your A. When starting to draw trump, play the J on the first round. If West takes it, you can ruff a diamond return in hand. Then, lay down your last high spade, cross to dummy in hearts and try the Q. If the suit splits 3-3 or East started with 9x, you can draw trump and claim. Dummy's 8 saves the day.

What if West ducks the J? Repeat the process by playing the 10 next (again, don't release the A). If West ducks, you lay down the A next and just run winners. If West takes his K and plays a diamond, you ruff in hand and proceed as above.

This is exactly how Sontag played it and this was the Real Deal:

Vul: Both Dir: North	Q872 AQ42 4 8542
K654 9876 Q109 QJ		93 103 AJ87653 K3
	AJ10 KJ5 K2 A10976

Spades weren't 3-3, but declarer was rewarded when the 4-2 break included East's 9x. Well played and plus 620 was a win on the board.