For the 4th month in a row, we visit the 2018 U.S. Team Trials. And, for the 4th month in a row, an expert's mistake cost big time. South held:

J5
76532
10
KQJ83.

Both vulnerable, his partner dealt and opened 1. RHO doubled and he chose an interesting 2. With the takeout doubler usually having hearts, I kind of like this off-beat action. You'll like it too when LHO bids 2(!) and your partner jumps to 5. RHO doubles and you play it there with a low spade lead:

Q76 -- AQ6432 A954
J5 76532 10 KQJ83

RHO wins the K and shifts to the 6. Declarer ran this to dummy's 9 and led a second spade. East won and forced dummy with a heart. Declarer (belatedly) played the A and a low diamond (the king falling from East). He crossed to the A, LHO showing out, to leave:

Q -- Q643 5
-- 7653 -- KQ

If everyone had followed on the second club, all would be good. Declarer would ruff a diamond in hand and dummy would be high (with the 5 as an entry via a heart ruff). However, East still had the 10. The diamonds weren't established (LHO still had 2 remaining). Declarer ended up down 2. This was the Real Deal:

Vul:Both Dlr: North	Q76 -- AQ6432 A954
10843 KJ94 9875 2					AK92 AQ108 KJ 1076
				J5 76532 10 KQJ83

Let's review the play. A spade was led to the king (double-dummy, only a trump lead sets the contract). The trump return went to dummy's 9, but declarer erred by playing a second spade. This allowed East to win and prematurely tap dummy.

At trick 3, declarer should work on diamonds. The A and a diamond ruff are followed by trump-drawing ending in dummy. The difference is that in this version, trumps are all drawn and dummy still has a trump remaining. Declarer sets up the diamonds with a ruff and then plays the J. East wins, but dummy is high (and still has a trump).