Partner doubled the weak 2S in reopening position in case you wanted to pass for penalties. Your spade holding was not quite up to that, but you liked your hand well enough to bid 3H, showing some values, rather than a lebensohl 2NT to show a weak hand. Having doubled 4H, North led the king of diamonds. How would you plan the play?
There are three obvious losers, a spade, a diamond and a heart. How can you avoid a second heart loser? Suppose you duck the first diamond and win the second, then run the eight of hearts. South follows, which is encouraging, and you play a second heart. This time North splits his honours and you win the ace as South discards a spade. If you now play a third heart North wins and forces dummy to ruff a diamond. You might play the queen of spades, but South wins and plays a club. You have no way back to hand to draw North’s last trump and must eventually lose one more trick.
Suppose you change tack after the first round of hearts and play a spade to the queen. South wins and returns a diamond for dummy to ruff. And you have the same problem – you cannot get back to hand to play another trump. The key to the hand is to discard your own third diamond on a club before playing a second heart from dummy towards your 10, 9 and 2.
North wins, but if he plays a diamond you can ruff high in hand and finesse against his remaining trump honour. He does no better if he plays a spade; South wins the ace but then must let you into hand with the king of spades or a diamond ruff to draw trumps.