Hands are from Adventures in Bridge, September 19, 2018.
South: ♠Q97 ♥K97 ♦7 ♣AKJ842
North: ♠AKJ ♥A108654 ♦Q1063 ♣—
It is difficult to get to a heart slam here, because you are missing one Key Card AND the Queen of trump, so most people would sign off. Our opponents' uncontested auction went: 1♥ 2♣; 2♦ 4♥. North could have tried a 4♠ control bid, but partner showing strength in your void is not encouraging, and your trump suit is anemic, especially if partner has only 3-card support. However, even if North bids 4♠ and South cue-bids 5♣, North has nothing more to say with two quick diamond losers. And, if South asks for Key Cards after North cue bids spades, South will discover they are missing one Key Card and the Queen, so slam is not favored.
I led a top-of-nothing spade (the unbid suit) and Declarer took it in the North. She pulled trumps in two rounds, ending in Dummy, and discarded two diamonds on the ♣AK. She then squandered Dummy's great club suit by giving up a diamond and making 12 tricks. She should ruff a LOW club. When the ♣Q ruffs out on the third round, she can discard ALL her losing diamonds on the good clubs. Even if the ♣Q had been in the hand with four clubs, Declarer should still make seven. Ruff third round of clubs. Go to Dummy with the ♠Q and ruff fourth round of clubs. Return to Dummy with the ♥9 and discard two more diamonds. At this point there is still one trump in your hand to cover Dummy's losing diamond.
North: ♠K953 ♥108 ♦K9875 ♣102
South: ♠4 ♥QJ9 ♦AQ10632 ♣QJ5
East opened 1♣ and South overcalled 1♦. West made a negative double, promising 4-4 in the majors. North raised to 2♦ and East cue bid 3♦: “You pick the major, partner,” which usually indicates equal length in the majors and caters to the possibility that the negative doubler has a strength disparity between the majors. South bid 4♦ and West and North passed, bouncing the major suit choice back to the 3♦ cue bidder who chose 4♥. Then it was pass, pass to North. N/S are white; E/W are red. Do you defend, or do you sacrifice?
The key is South's bid of 4♦. South should NOT bid 4♦ unless she is willing to defend four of a major. (Just like I tell my students when hearts and spades are battling it out: “Don't bid 3♠ unless you're willing to defend 4♥.” and “Don't bid 4♥ unless you are willing to defend 4♠.” Do NOT push the opponents into a possibly making game.) So, if partner is willing to defend, you should be willing to defend, and not take the sacrifice. As it is, 5♦* is down only three, which is OK against a making vulnerable game; however, 4♥ is down one. Trust your partner.
The full hand was:
The auction at our table went: Pass by East, 1♦ by South; Pass; 1♠; Double by East (guaranteeing at least 4-4 in the two unbid suits and close to an opening hand); 2♣ by South; 2♥ by West; 3♦ by North; pass; pass; pass. When someone bids both minors as South did, they usually have a singleton—most often in their partner's suit. That is something to bear in mind when defending. In this case, I would expect South to be 5-5 because she has bid clubs (her second suit) in the teeth of East promising four cards in the suit! West led the ♣10, and partner took the ♣A. After surveying Dummy, East switched to the ♥3 (her lowest—so bottom of something). West won the ♥Q while South false-carded with the ♥J.
The proper card to play next is the ♥A. Partner does NOT have five hearts on this auction because (a) she might have bid 2♥ instead of doubling if she had five; (b) she led her LOWEST heart, the ♥3—the 2♥ is visible in Dummy—so she has exactly four hearts. [With five hearts, she would have led fourth-best and there would be a lower spot card missing in action.] Her ♣A denied the ♣K. If you do not take your second heart trick now, it will disappear on the second high spade in Dummy.