This deal is from a Regional Knockout Teams during the 2013 St. Louis NABC. With both sides vulnerable, East held:

KQ10
Q2
K43
A8432
 

His LHO deals and opens 1. Partner passes and RHO responds 1. This is alerted as showing at least 5 cards in spades (people who use Flannery usually have this agreement). Are you coming in? No, the water is not fine. This is the wrong hand to even think of making a vulnerable 2-level overcall between two bidding opponents. Your suit is horrible. A takeout double or strong notrump overcall is equally dangerous and counter-indicated by this flat 5-3-3-2 hand (not to mention the Qx in LHO's suit).  After your pass, LHO rebids 2.  RHO invites with 3 and LHO goes to the heart game. Partner leads the J (standard) and you see.

Vul: Both Dlr: South	A7532 87 AJ97 76
-- -- -- --		KQT Q2 K43 A8432
	-- -- -- --

On your A, declarer drops the K. This isn't a very wise falsecard, because you already know from partner's lead that he doesn't have the Q.  Now, you know declarer has KQ doubleton. If you are ever declarer in this situation, remember to to drop the queen and hide the king (the person who wins the ace might think the lead was from KJ109).

Anyway, after winning your A, how will you continue?

Your diamond spots are troublesome. If declarer works on that suit, he can likely set up discards for any spade losers he has. Accordingly, you should shift to the K in an attempt to establish a spade trick for the defense. This would cost a spade trick only if declarer has Jxx, but with that holding, he would have raised spades at some point.

On your K, everyone follows low. Now what? If declarer has a doubleton spade (as it seems), he will be able to play the A on the 2nd round of the suit and then set them up with a ruff. So, you need to dislodge the diamond entry from dummy. You need to get off the Spade Horse and get on the Diamond Horse. You will need your partner to have the Q and a trump trick as well, but it is your only chance. This was the Real Deal:

Vul: Both Dlr: South	A7532 87 AJ97 76
986 J43 Q65 JT95		KQT Q2 K43 A8432
	J4 AKT965 T82 KQ

As you can see, your defense (A, K, low diamond) was the only winning order of plays. Your side gets one trick in each suit for down one. Notice the aggressive bidding by North-South, but these days you can expect your vulnerable opponents at IMPs to put the pressure on you. Had you done anything else, declarer could easily have succeeded. He could play the AK and then work on diamonds, eventually throwing a spade loser on dummy's fourth diamond. The dummy's spots in diamonds and spades were your clue to the winning (but not easy) defense.