The auction is simpler than it looks. North’s five-heart bid asked for the queen of trumps and South’s six-club response promised the spade queen plus the king of clubs. The sixdiamond continuation was a grandslam try which South rejected.
South covered the jack of hearts lead with dummy’s queen, reasoning that he would make his slam if West started with either the king of hearts or the king of diamonds. When East proved to have both of those kings, the contract was defeated. South should have put some effort into analyzing the opening lead. Would West have led from a king after an auction where his opponents were looking for a grand slam? An auction like this calls for a passive lead and West leading from a king was most unlikely.
A better play would be to play low from dummy at trick one, winning immediately if East had a singleton king. Assuming no king of hearts appeared, South should draw trumps, eliminate the clubs from both hands, and exit with a heart to the queen. East would win but would have to lead a diamond or yield a ruff-sluff – 12 tricks either way. Should East have a third club to lead, South can still try the diamond finesse for his contract.
