The bidding:
South, with 15 HCP and five spades, opens one spade. The quality of the suit should not deter one from opening one spade. With spades as trump, even little spades can be useful ruffing.
Although one may open one spade with five little spades, such a suit is not recommended for an overcall. To overcall one spade, one needs a suit that can easily draw trump.
Whether opening one spade or overcalling one spade, one is giving partner lead direction. As lead direction, the spade suit headed by the nine is very poor, but declaring a spade contract with AKJ10 in dummy makes the risk worth it.
North has an opener himself with spade support. He may bid a new suit at the two level and then jump to game. He cannot jump directly to four spades, because that shows a weak hand.
Jacoby 2NT is another bid that is available. A bid of 2NT in response to one of a major shows at least an opening hand with four-card support. It also denies a singleton or void at the same time asking partner to show his shortness.
South replies three clubs which shows a singleton or void. This makes North happy because he has no wasted honours, king through jack, opposite the singleton.
North then asks for keycards just to make sure two are not missing. South shows two keycards and then two kings. Five spades are cold so asking for keycards is not risky at all. However, North discovers they have enough for seven spades. He has the ace and king of hearts and diamonds and with three club ruffs, there are thirteen tricks.
The contract: Seven spades by South
The opening lead: The queen of clubs
The play:
Declarer wins the ace of clubs and draws trump at the same time as ruffing clubs. If the trump are two-two, the contract is straightforward. The critical part of the whole contract is the three-club bid. If trump split three-one, care must be taken to get three club ruffs before drawing trump.
The result: Seven spades making for +2210.
Note: Without Jacoby 2NT, it becomes a lot harder to get to seven. Jacoby is a valuable tool that should be discussed with one’s partners and added to one’s arsenal.