This deal comes from the Sarasota-Manatee Regional in 2014. South held:

32
AJ987
K92
AK2
. With both sides vulnerable in a knockout match, his partner dealt and opened 1. South responded 2, natural and game forcing. Opener rebid 2 (presumably showing 6 or more spades).  I don't like raising spades with only two, much preferring 2NT with a hand like South's.  North now jumps to 4. What does that mean? In the 2/1 GF system, jumps to game in previously bid suits are the weakest actions. North is showing a minimum with no slam interest. South has nice controls, but if slam was in North's thinking, he should have bid only 3.  South doesn't have enough extras to make another move. The J is led and dummy tables:

AQ8754 KQ10 875 4

32 AJ987 K92 AK2

I've been in worse slams. If both majors behave, it is possible that six hearts will make. But, this declarer was in only 4. Follow his thinking and see if you can figure out where he went wrong. He took the first two tricks with the AK, throwing a low diamond from dummy. Next he took a spade finesse, the Q losing to the king. East played back a high club, ruffed in dummy. Declarer, now unable to set up and use spades (dummy had only 2 trumps remaining), changed tac. He had already lost a spade trick and still had K92. He led towards his K, but that lost to the ace and LHO nastily switched to a trump. Another diamond begot another trump from the defense. In the end, declarer had to lose a 3rd diamond trick for down 1.

Where did he go wrong? Taking the first 2 clubs (throwing a diamond) followed by a spade finesse was a reasonable start. Nothing else is obviously any better. The mistake came after East took the K and played a high club. On this trick, declarer should have thrown a diamond from dummy! This beautiful loser-on-loser play gives the defense no answer. Here was the Real Deal:

Vul: Both Dlr: North	AQ8754 KQ10 875 4
109 654 AQ3 JT853		KJ6 32 J1064 Q976
	32 AJ987 K92 AK2

After declarer throws dummy's second diamond, what can the defense do? If they switch to trump, declarer sets up spades and draws trump ending in dummy. If they play more clubs, declarer can ruff in hand, set up spades and again draw trump ending in dummy. Lastly, if the defense plays diamonds, declarer gets to ruff his third diamond in dummy, losing only 2 minor-suit tricks. Credit David Berkowitz and Alan Sontag for the accurate defense (benefiting when declarer went wrong).