North orders the king of spades into his partner's hand.
South discards the queen of spades. Then:
West starts the hand by leading the ace of hearts.
North and east follow suit, south trumps in with the ten.
Next South leads the right, showing North where it is. West throws off the ten of hearts, North plays the nine of trump, and East throws off the ten of diamonds.
Trying to set up the king, South leads the nine of diamonds, West plays the ace, North trumps with the queen, and East throws off the nine of clubs.
Now we are at the critical fourth trick. Yes, leading the left would give their team a sure point, but why not go for two points?