From actual play (June 10, 2009). Matchpoints. Your opponents are not adept.
The auction is:
pd RHO you LHO
1C 1D 1H 2D
X(1) 3D P P
(1) support double, showing exactly 3 hearts.
You lead the J and dummy comes down with
This looks at first like a disasterous lead, but declarer plays the Q and partner plays the K, which holds. Partner shifts to a small trump. Perhaps he is trying to get the trump off the board. When declarer plays low, you win the ace. Lacking any other attractive options, you return a trump. Maybe partner knows what he is doing.
Declarer draws partner's last trump. You play a heart. Declarer now rattles off three club tricks -- Q, A, and K -- on which your partner drops the ten and the jack. (Your partner would play the Jack and 9 from J109.) Good thing you saved a club.
Declarer now plays a small heart. The situation looks like this.
Count the hand, then click here
Declarer has to have 5 diamonds. Declarer almost certainly has 4 clubs, and can have only 2 hearts, because partner has to have 3. That gives declarer 2 spades. If they are AK, or Ax, it doesn't matter what you do. If it is Kx, you would like declarer to have to lead from her hand.
So you might as well play for declarer to have Kx. But in fact, partner has shown 8 HCP so far. He almost certainly has 12 HCP for his bidding, placing him with the ace of hearts; he almost certainly doesn't have 15 HCP, giving declarer the king.
So the situation is this
Now you have to figure out what to do when declarer leads a heart from hand. Plan out the defense, then click here
If you allow partner to win this, partner might lead a spade. If he doesn't, the declarer has to ruff the heart. The problem is, declarer can now lead a club to endplay you into leading spades.
So now the correct defense appears. It is not particularly counterintuitive, so full credit only if you knew what you were doing and why. You have to rise with the 10 of hearts and cash your winning club, so that declarer cannot endplay you. Then you exit in hearts and declarer will have to lead away from the Kx of spades.