This conundrum was written by Eddie Kantar and was originally published in the book Kantar for the Defense - Volume 2 - you can find out all about it further down the page.
Both sides vulnerable
Dealer North
Opening Lead: ♦J
Dummy wins, partner signals with the ♦9, and declarer follows with the ♦3. A spade is led to the ace, followed by the ♥Q and a heart to dummy. Partner follows with the ♥5 and the ♥4 as you discard a diamond.
At trick five the ♠Q is led from dummy, declarer discarding the♦Q.
Do you win this trick? If so, what do you return? If not, why not?
Crediting partner with three trumps (from his high-low count signal in hearts), it is possible to count declarer's tricks.
If you win this trick and return a spade, say, killing one discard, declarer will remain with six trump tricks, four spades, plus two minor suit aces for twelve. (Declarer must have the ♣A to have any play.)
What about ducking this trick? If declarer plays another middle spade, partner ruffs and the spade suit in dummy is dead. Now all partner needs is the ♣K to defeat the contract. The proper play is to allow the ♠Q to hold so that partner can trump the next spade, killing dummy's long suit.
1- Partner's willingness or failure to double to high level cue bids should influence your choice of opening leads.
2 - One technique of killing a long side suit in dummy is to delay taking your winner until partner is void. Then he trumps the suit allowing you to retain your winner.
3 - If the deuce and trey of trumps are interchanged, this hand cannot be defeated! Declarer cashes the ♠A at trick two, crosses to the ♥A and leads the ♠Q. The defense is helpless because there is an additional dummy entry. Work it out.
Kantar invites his reader to direct every play towards the goal of beating the contract in a variety of hands, bringing focus on counting tricks, points and distribution. Problems range from an intermediate to semi-advanced level and knowledge of basic card combinations is assumed. Each book concludes with a complete list of themes for its 100 problems.