The other day, I was talking to Kaustabh Nandi when he gave me a 3NT hand he had played.
Here's the hand, South to play 3NT on a small Heart lead:
♠ 93
♥ A4
♦ AQ1073
♣ A873
♠ Q42
♥ K105
♦ KJ84
♣ QJ4
Looks easy enough. You have 2 hearts, 5 diamonds and a club off the top. If the lead is from QJxx, you have 9 tricks on opening lead. Otherwise, win the first trick and finesse in clubs.
This made me very uncomfortable. When Nandi gives you a hand, its never straight-forward. What was the catch? I couldn't see it.. Run the Diamonds? what good could that do? Only 6 cards would be played, and opponents would have plenty of room left.
"What was the auction?" I asked, hoping to buy some time. "Not relevant. 1♣ - 1♦; 1NT - 3NT". Some more silence. "I give up. What did you do?"
Kaustabh explained - "I played small from dummy, and when RHO produced the Jack, I ducked! RHO backed a heart to dummy's Ace. The spots indicated that LHO had started with 5 hearts. I crossed over to hand in Diamonds and tried the Club finesse. To my relief, it lost. When RHO now triumphantly produced his third heart, I claimed!"
"So, had the club finesse been on, you had gone down in a cold contract?" I asked him. "Not really", he replied. "Who would believe it? Who would shift to a spade after their ♥J held? Would you have?"
No, I wouldn't have.