This deal was played in the 2016 Southeastern Regional in Florida . East held:

 Q9853  
 83  
 Q95  
 AJ3.

In a knockout match with both sides vulnerable, his partner dealt and opened 4. This was followed by two passes and 5 by LHO! What's that? Presumably spades and a minor--a high-level Michaels bid. RHO bid 5NT (pick a minor) and LHO chose 6. With spades and clubs well controlled combined with partner's vulnerable 4-level opening, East chose to double.

The K was led and East saw:

J2  642  J642  Q842
	Q9853  83  Q95  AJ3

Declarer won the A and cashed the A (partner playing low). Next came a low club, partner throwing a heart. Dummy plays the queen and it is up to you.

Suppose you win the A. What next?

From the bidding and play, you know everyone's cards. Declarer must have 5 spades and 6 clubs and the two singleton aces in the red suits. Since we are now "double-dummy" let's look at all 4 hands.

Vul:Both Dlr: West	J2  642  J642  Q842
4  KQJ10975  K10873  --		Q9853  83  Q95  AJ3
	AK1076 A A K109765

Did you figure out to return the J? If you play a low club, declarer has a marked finesse and can win in dummy with the 8.

He would have only 2 trumps left in dummy, but could make his contract by leading the J for a finesse. He would then have to ruff only 2 spades in dummy. Would he play this way? Maybe. The 4 opening (combined with the trump return) could point the way.

Why give him the chance? If you return the jack of clubs, he has to win in his hand. Then he can take the ace-king of spades and trump two spades in dummy, but will have to lose a spade trick at the end.

The J is a sure thing (to set the contract), but maybe you are wondering why you have to play any trump? Look what happens if you play anything else. If you lead from the Q, declarer can finesse. If you lead a red suit, he trumps in his hand, cashes the high spades and has a complete crossruff for 12 tricks.

At the other table, South didn't come alive with his 6-5. He overcalled 4 and went down 3 tricks for -300.