East, who had been suffering a long succession of poor hands, chose a good moment to indulge in a first in hand psyche (a dangerous manoeuvre) when he opened One Heart. Unwilling to be shut out, with an unsuitable hand for a double and short of points for a 1 no-trumps overcall, South elected to join in with One Spade. Now 3 no-trumps (ideally played by North) would have been the best contract but, not unnaturally, North placed his partner with longer spades and the final contract was Four Spades.
West led !8 and (although in practice the king would have worked well) declarer played low from dummy and won with his queen. He continued with 4J and 4A but, when West followed with the seven and eight, he stopped to think. If the trumps did not break, the side suit had to be established while dummy still held a trump to take care of a possible fourth round of hearts. (By this time he was a little suspicious of East's opening bid.) Instead of another trump, South led #10 and West covered with his queen. Declarer went up with dummy's ace and continued with #3.
East placed his partner with #K and the normal play would be to discard. However, East realised that if he let West win with #K his partner would not be able both to give him a ruff and lead through !K. So East ruffed the diamond and exited with a club. Now when West got in with #K he continued hearts to defeat the contract.