Niccolo Machiavelli, an Italian who is famous for writing "The Prince," said, "Ambition is so powerful a passion in the human breast that however high we reach, we are never satisfied."
At the bridge table, we must decide how high we wish to reach. In this deal, North opens one diamond, South responds one spade, and North raises to three spades (yes, he might bid four spades). Now South normally has three choices. He can pass with no interest in game. He can raise to four spades. Any other suit bid shows interest in a slam.
Here, four diamonds is a control-bid (cue-bid), usually indicating the ace. However, since it is partner's first-bid suit, South might have only the diamond king when he does not have the club ace. (Do not make your first control-bid with a shortage -- void or singleton -- in partner's second suit.)
North then control-bid four hearts. (If North-South had been using Roman Key-Card Blackwood, North would have bid four no-trump.) This allowed South to use Blackwood twice before jumping to seven spades. (Yes, South might have bid seven no-trump.)
West leads the club queen.
After winning trick one with his king, South cashes the spade ace, getting the bad news. Now he crosses to dummy's club ace and plays the spade nine, capturing East's 10 with his king. Back to the board with a heart, another spade through East picks up his trumps and allows declarer to claim.