After you bid 2♥ over East’s 1♠ bid, your partner asked for key cards with 4NT. When you showed two key cards plus the ♥Q, North made a grand slam try by bidding 5NT, guaranteeing all the key cards and the trump queen. He was hoping you would show the ♦K. When you denied holding that card by bidding 6♥, your partner gave up on the grand slam. West started with the third-highest ♠3. You take trick one in dummy perforce. Now what?
After winning the first trick with the ♠A, declarer cashed the ace of trumps to make sure that trumps were not 5-0. When both opponents followed, declarer decided to try to set up dummy’s long suit, the diamonds. Rather than risk the tempting diamond finesse, declarer played the ♦A and another diamond. After winning with the ♦J, East forced dummy by playing a high spade.
Declarer ruffed this with the ♥9, then drew a second round of trumps with dummy’s 10. Next, he ruffed a diamond high, thereby establishing the suit. All that remained for declarer was to draw West’s two remaining trumps and claim 12 tricks: one spade, a spade ruff, five trumps, two clubs and three diamonds. The full deal: