The Best Chance

Dlr: North ♠ 6 4
Vul: E-W 8 6 4 2
A K Q 3
♣ K 6 3
♠ A K Q J 9 3
3
8 6 4 2
♣ J 4
West North East South
1 Pass 1♠
Pass 1NT Pass 4♠
All Pass

Against your 4♠ contract, West starts with the top two hearts. You ruff the second round and now must decide on a plan to get to 10 tricks. Do you have any ideas?

Solution

After ruffing the second heart, declarer drew trumps in three rounds, throwing a heart from the table. Declarer saw that he would always have 10 tricks if diamonds were 3-2 or West had the ♣A, so he considered what could be done if both of these possibilities failed. He saw that the only hope in such circumstances was that East had ♣Q. Accordingly, he crossed to dummy with the A diamonds and led a low club toward his hand. East rose with the ♣Q and led a third heart. Declarer ruffed and led the ♣J, which was taken by East with the ace. (South was pleased to see that East had that card, too.) East continued with a fourth round of hearts; declarer ruffed in hand and threw the *D*3 from dummy. He then played a diamond to the king and was pleased to see East discard a club. Declarer made six trumps, three diamonds and a club for a total of 10 tricks.
You should note that nothing is lost by the approach of not playing a second diamond when West turns up with the ♣Q. You can still have the original chances of the ♣A being onside or diamonds being 3-2.
The danger of playing a second diamond before leading a low club can be seen just by transferring the ♣A and ♣Q to West: West wins with the ♣Q and plays a third round of diamonds, making the ♣K unreachable. West would make a heart, two clubs and a diamond. The full deal:

Dlr: North ♠ 6 4
Vul: E-W 8 6 4 2
A K Q 3
♣ K 6 3
♠ 10 2 ♠ 8 7 5
A K J 5 Q 10 9 7
J 9 7 5 10
♣ 10 8 5 ♣ A Q 9 7 2
♠ A K Q J 9 3
3
8 6 4 2
♣ J 4