I had a real problem, when I had to decide, that it should be a 26 cards problem, where only West's and North's hands are visible, or a double dummy problem, when I started writing tis article. I made my decision, and I hope, thet many of you were thinking a lot to solve it, because it worth wasting the time to come to the following solution:
As it was given as a starting point, the opening lead is the King of diamonds, the declarer wins it with the Ace, plays spade to the King and spade to the Jack, and he plays a small heart to the King, partner gives the 2 of hearts, showing even number in the suit.
The first mission is to identify the problem, which is not so easy this time.
We can assume from the bidding, and the probably single Jack of diamonds coming from the declarer, and the two of hearts from partner in this trick, that declarer has 5 spades, 3 hearts, singleton diamond and 4 clubs.
When we win this trick with the Ace, and play our Queen of diamonds (or any other card), declarer ruffs it in his hand, he takes the trumps in 2 more rounds, than he plays a small heart to the dummy's Jack, he plays the Jack of clubs, partner has to duck it, now he plays the ten of clubs, partner has to cover it, now the declarer is in his hand in the following endplay:
Now, when the declarer plays the six of hearts, and wins it with the Queen in the dummy, West doesn't have minor cards, so East will be squeezed: he either discards the ten of diamonds and the small diamond on the dummy will be good, or he discards one of his clubs, this way the clubs in the hand will be good.
It worth recognizing, that East was squeezed, because we didn't have good diamond in our hand. It doesn't help unfortunately, when we play another card, let's assume spade.
Now the declarer wins the 3rd round of spades in the dummy, than he plays the Jack of clubs, partner has to duck it, now he plays the ten of clubs, partner has to cover it, now the declarer is in his hand in the following endplay:
Now declarer goes to the dummy, and ruffs a diamond in his hand, so he reaches, that only East will have clubs and diamonds and he cashes the last trump from the hand, reaching the same 3 cards squeeze situation as above.
The only solution is, that West has to duckthe King of clubs. Now the declarer still can go to the dummy with the Queen, and ruff the 2nd round of diamond. He has to cash the last spade from hand and we come to the following 6 cards end-play:
Now the declarer is in his hand,and he has to play heart to reach the dummy.
And it is the time for West to defeat the contract. When he loses his nerves and wins the 2nd round of hearts, he can play only club or heart, both can be won at the dummy,and East will be squeezed at the 3rd round of hearts.
So West has to duck the 2nd round of hearts! Now, the declarer is at the dummy for the the last time, and he couldn't rectify the count for the squeeze. East is not forced to discard a minor card to the 3rd round of heart, so his only mission is now to cover only the 2nd high card in club, because than he surely wins the last card in clubs.
The declarer is destroyed this way, because there are no more trumps in his hand, so he has to play the club finesse to take 11 tricks only and a score far below average.