This double-dummy problem was composed many years ago by Sidney Lenz. The object is to make Seven Hearts against the queen-of-clubs lead. Best defense is assumed, and, of course, declarer is allowed to see all 52 cards.
Win the queen of clubs with the king, discarding a diamond, and continue with the ace of clubs. Then:
1. If East ruffs, overruff, cash the ace of spades and lead the queen through West’s king. West must play the king of spades on this trick or the next one, whereupon you ruff in dummy and finesse the 10 of trumps to score the rest of the tricks.
2. If East discards a spade on the ace of clubs, trump the ace, play the A-Q of spades as before and take a trump finesse.
Then cash your remaining spade or spades, enter dummy with a diamond to the king and ruff another club, reducing your hand to the A-K-J of trumps and nine of diamonds.
Lead a diamond to the ace, lead anything at all from dummy, and East’s Q-7-6 of trumps succumb to your A-K-J.
3. If East discards a diamond on the ace of clubs, discard your nine of spades and take a trump finesse. Then enter dummy with a diamond and repeat the trump finesse. After you cash the A-K of trumps, this becomes the position:
When you now play the four of hearts, West can discard the 10 of clubs as dummy also discards a club, but when you next play the three of hearts, West is caught in a three-suit squeeze. No matter which suit he discards, the rest of the tricks are yours.
Tomorrow: Now you see it, now you don’t.