Rarely is a hand dealt in bridge that does not offer a chance to use the powers of deduction for which Sherlock Holmes was remarkable. He could have made a formidable reputation at the card table, even without the ubiquitous Dr. Watson to remind the world of his exploits. Minus a Watson of my own, I am forced, modestly, to serve as my own commentator in the following hand, which I defended many years ago. You can share the mystery that confronted me with East's hand if you cover the West and South cards.
It doesn't greatly affect your problem with East's hand, but let me warn you that in the days when this hand was dealt a player opened the top of partner's bid suit even if he held three to an honor. So, when West continued by leading the spade 3 to your ace at the second trick, with South having dropped the 5 and 7, it was quite possible that your partner held the still-missing deuce.
It is at this point that you are invited to take over the defense. What do you know about South's hand? How are you going to play to beat him?
Surely the setting trick must come from the club suit. "Correct," Holmes might have said cryptically, "so of course you return the jack of hearts!"
South's bidding reveals a strong hand. His jump rebid in diamonds before he showed the clubs announces a great disparity in the length of these suits: at least six diamonds and only four clubs. And, when dummy turns up with the diamond king, it is a virtual certainty that the diamond suit is solid. South had already followed to two spades, so you know the location of all but one of his cards. If his remaining card is the missing spade, no return will make any difference. If it is a heart, it is essential that you remove it from his hand at once.
Return the jack of hearts and you will see what happens if you now uncover the South and West hands. Dummy wins the trick and declarer can take a club discard on the ace of hearts. But he will be unable to establish the heart suit for another discard and sooner or later he will have to lose a trick to West's queen of clubs.
What would happen if, in the knowledge that a club trick must be won, you attack that suit directly instead of leading the jack of hearts? You might set the contract anyway—but not if South guesses the right way to play for it.
He wins the club with the ace, leads out all six trumps and forces West to find three discards. West can afford to throw one heart and the last spade. But the final trump compels him to choose between establishing dummy's heart suit or unguarding his queen of clubs. The latter is the better choice, since it forces declarer at least to a guess. But the chances are that declarer, if he is a seasoned operator, will guess correctly—if only because he prefers to win by a squeeze rather than by a simple finesse.
Even when the source of the setting trick becomes obvious, attacking that suit may not be the best way to insure cashing in. Stop and count declarer's hand. The solution of the problem is often found right there.