Dormer on Discovery

Readers of my series on deduction may, on occasion, have experienced a certain feeling of impatience as they were repeatedly advised to try to employ deductions from what the opponents had or had not bid, played or discarded. “This is all very fine and good,” the reader may have found himself muttering, “but what do I do when the opponents haven’t entered the building, haven’t shown out of any important suits, and haven’t disclosed any real information that I can work on?”
Since this is the case on a great many deals, I will not deny that there are times when information is sadly lacking. But this doesn’t mean that you should throw up your hands and pray that the gods of chance will be kind to you; it simply means that you should go right out and discover the information that you need. Plays made with this object in mind are called discovery plays, and a knowledge of them is essential to any fine declarer.
The general idea is that when there is more than one way to approach the play of the hand, you should select the line that is likely to tell you the most about the defenders holdings. For example, take this situation:

 North (Dummy)
A Q x x
South (Declarer)
J 10 x

Let’s assume you are playing a trump contract and that this is a plain suit. Assume also, for reasons we needn’t go into, you want to know — before attacking trumps — whether the finesse is going to win. Now, if you simply lead the jack, which may seem a perfectly normal thing to do, and it holds, you will not be very much wiser. Perhaps West has the king and everything is going to turn out all right for you. But then again, maybe East has the king, and is holding it up because he can see that it cannot cost him to do so.
Moreover, you cannot resolve the matter by taking another finesse in the suit. Such a procedure would be highly dangerous, for you could run into a ruff if West had a doubleton. Therefore you have to abandon the suit temporarily, having failed in your objective of finding out who has the king.
However, the situation would be quite different if you started the suit by leading low from your hand and finessing the queen, In this case, if the queen held the trick, you could be sure West had the king. East would not hold up the king if he had it, for he would look like a chump whenever you didn’t have the jack.
In short, leading low to the queen on the first round is a far better form of discovery play than leading the jack, since it figures to elicit more information.
Discovery plays may be made with a deeper purpose than simply to ascertain the layout of a single suit. Here is an example where declarer makes a discovery play in one suit in order to avoid a guess in another suit:

 Dlr: North North
 Vul: None ♠ K Q 4
A 6 3 2
8 7 5 3
♣ 8 2
♠ 7 2
Q J 10 9 7 5
J 4
♣ K J 10
West North East South
Pass Pass 2 All Pass

You are South and you open with a weak 2 bid which is passed out. West leads the K, East encourages, and West continues with a low diamond to East’s ace. East returns the 2 which you ruff as West follows suit.

At this stage you can’t really tell whether you are going to make the contract: if the fates are unkind, you could lose two clubs, a trump and a spade in addition to the two diamonds you have already lost. Be that as it may, the heart finesse is first in the order of priorities, and so you lead the Q and let it ride. When this holds as East follows low, you become certain of making the contract. Now you can begin to consider the next item on the agenda, which is to give yourself the best possible chance of making an overtrick.

When you examine the black suits, you notice that although you might wind up making two spade tricks if West has the ace, this really makes little difference to the outcome of the hand. Even if you score two spade tricks, you can park only one club on the second one, and you will still be left with the task of trying to avoid two club losers.

Therefore, the location of the ♠A hardly seems to matter. The big thing is whether when a club is led, either from the dummy or by East, you are going to play the jack or the king. That is what will make or break your matchpoint score, and the question is, how on earth can you deduce the club layout?

So far, West has shown up with the KQ and the K, while East has turned up with the A. Once you begin to think along these lines, you realize that you would be a whole lot better off if you knew where the ♠A was. It doesn’t matter who has it — but it would help to know before you commit yourself in the club suit.

Accordingly, after having drawn West’s king of trumps with the ace, the next move should be to lead the ♠K. On this round, or the next, you will learn who has the ace.

Suppose West has it. In this case you intend to play East for the ♣A, for West will have already shown up with an ace, two kings and a queen, and if he had the ♣A in addition, he surely would have taken some kind of action over 2.

Alternatively, if East turns up with the ♠A, in addition to the A, you intend to play him for the ♣Q rather than the ace. This conclusion is reached by inferring that if East had begun with three aces, along with a singleton heart, he might well have opened the bidding.

Thus the discovery play of finding out which defender has the ♠A is the key to the hand, even though you hardly care how many spade tricks you make. This is the kind of technique that will be covered in this series.

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