Some plays are so well-known that when the opportunity to use one of them arises, there is a tendency to make the play automatically, without pause for thought. This is a somewhat dangerous practice, since what is right on most occasions might easily be wrong on a particular deal.

Take this case where West led the king of hearts against three notrump. Recognizing the chance for a “Bath Coup,” declarer allowed West’s king to hold the trick, hoping West would continue with a heart into the A-J. Unfortunately, this was a case where the cure proved worse than the disease.

Warned against a heart continuation by partner’s discouraging deuce, West switched to the spade queen. South ducked, but when West continued with the jack, covered by East with the king, declarer was well on his way to irreversible defeat. If he ducked the king, East would return a heart through the A-J, while if he won the trick, the defenders would finish with three spades, a heart and the diamond king for down one.

South should have realized that ducking the heart king in this case was wrong for two reasons. First, West was very likely to shift to a spade; second, South was in a position to guarantee a minimum of nine tricks if he took the first trick with the ace. He would then cross to dummy with a club and lead the diamond queen.

If East had the king and did not cover, the finesse could be repeated to yield at least three diamond tricks. And if the finesse lost to West, declarer, with the J-5 of hearts serving as a stopper, would have nine ironclad tricks consisting of three diamonds, four clubs and the two major-suit aces.

All of which goes to prove once again that a little knowledge can sometimes be a dangerous thing.

Tomorrow: Bidding quiz.