If you study all four hands, it might seem that declarer must go down either one or two tricks at four hearts. But South made the contract, and, furthermore, the defenders could do nothing to prevent it.
West started by leading the nine of clubs — top of a doubleton — and South, taking full advantage of West’s vulnerable spade overcall, proceeded to play the hand as if he could see through the backs of the cards. After following low from dummy, South won East’s jack with the ace, drew three rounds of trumps and then played a club to the king.
Having run West out of hearts and clubs, declarer now led a low spade from dummy. He planned to play the ten if East followed low in order to force a favorable return from West.
But East, anticipating South’s intentions, put up the jack of spades in an effort to thwart the impending endplay. This well-intentioned move by East went for naught, though, since South, holding the K-10-2, simply covered the jack with the king, losing to West’s ace.
West did as well as he could when he cashed the queen of spades and exited with a spade to South’s ten. However, this provided West with only a temporary reprieve, because South countered by playing the ace and another diamond.
Back on lead with the king of diamonds, West once again found his position untenable. It didn’t matter whether he returned a spade or a diamond; in either case, South would ruff in dummy and discard the ten of clubs from his hand to make the contract.