After trick one, declarer has a complete count. East is void in the black suits when he doesn’t ruff the ♣A. The absence of a diamond lead strongly suggests a diamond void with West, so East’s distribution is 0=4=9=0. The only mystery is the location of the heart honors.
South’s goal is to score five red-suit tricks to accompany his six spades and one club. For you to make four heart tricks, West must hold ♥Q 10 x. A finesse of dummy’s jack and an unblock of the king pave the way. The danger is losing control, however, because South must use all his trumps to pull West’s. How does South create an extra entry to his hand to cash the ♥A 9?
The key is to utilize the ♦Q. When declarer pulls trumps, he must jettison dummy’s ♦A. Next, finesse the ♥J, unblock the king and lead a diamond in the four-card ending below:
East–West cannot stop South from winning three of the last four tricks. If West drops the ♥Q on the second round, the card he is known to hold,
he retains the 10 in the diagram above. Declarer should not go wrong in the ending because the count tells him that West must hold another (equal-size) heart.
The fancy unblock in diamonds and heart assumptions are necessary. Suppose declarer aims for a different ending, hoping that East holds the ♥Q, with or without the 10:
A strip-squeeze against East is due to fail. Say declarer leads a heart to dummy’s king and advances the jack. With either heart holding, East can cover. If South ducks, a heart exit assures a diamond trick for the defense. If South wins, he must either allow West on lead with the ♥10 to cash clubs or trade heart tricks with East and eventually play diamonds, losing to the king.
In effect, this beautiful puzzle is like a double-dummy exercise, except that declarer must first visualize the necessary distribution, and then analyze how to exploit it.
