South did the wrong thing on this deal, and my partner did very well to take advantage.
We play a strong-club system, and open four-card majors ahead of five-card minors, so we found our heart fit at once. Against 3, North led out two top clubs, South pitching a diamond and declarer ruffing. Declarer played a spade to the queen and ace, noting North's 2 showing odd count. South cashed A and continued spades; declarer finessed, cashed his remaining spade, cashed K, and ruffed a diamond. Now a club, ruffed and over-ruffed with A, a diamond ruff, and a club exit to endplay South.
Declarer reasoned that North's apparently painless decision to continue clubs at trick two suggested that she didn't have short spades. South simplified the play by cashing A, but his decisive mistake was the diamond discard at trick two. He should have thrown a spade (or he can ruff in). That's a difficult play to find - why shouldn't partner have 9xx - but a logical one: you can beat the contract with three aces and two trump tricks, and shortening your spades guarantees the trump tricks.