On some deals, a defender will have a dilemma, not sure how to defeat the contract. He must rely on his partner.
Against five diamonds, West leads the spade two. How should declarer play? Suppose he wins with his ace, plays a heart to dummy’s 10, and runs the diamond nine to West’s king. How should West defend?
After two passes, East opened a light third-in-hand one spade. South overcalled two diamonds. West made a pre-emptive jump to three spades, showing four-card support and less than game-invitational values. (With a stronger hand, he would have cue-bid three diamonds.) North doubled to indicate a maximum pass, and South jumped to five diamonds.
This is a difficult deal. It is tempting for declarer to assume that East holds the diamond king. But after the diamond finesse fails, West wonders whether his side needs to take one diamond, one spade (when East has only five spades) and one club, or one diamond and two clubs (when East has six spades). He does not know, but East should. At trick four, West should shift to his club queen, and South plays low from the board. Now the spotlight is on East. From the spade-two lead, he knows that West has only four spades. So East should overtake with his club ace and cash the spade king.
What did declarer do wrong? It is better to cash his diamond ace at trick two. If the king drops, fine. But when it does not, South turns to hearts, getting home if the defender with the diamond king has at least three hearts. Declarer’s club loser evaporates on dummy’s fourth heart.