Yesterday we looked at takeout doubles over an opposing pre-empt at the three-level. But what about your double over a four-level opening in a suit? What does that mean?
Now we are entering very murky waters. The first thing to bear in mind is that a four-no-trump overcall is not natural, but is usually treated as showing a big two-suited hand. This means that a takeout double just says that you had too many points to pass, but had no better intervention to make. You have anything from a three-suiter short in the opener's suit to a balanced hand with at least, say, 15 high-card points.
How does the advancer (doubler's partner) react? He bids a long suit, perhaps with a jump if he has a strong hand; or he passes, hoping to extract a pleasant penalty. It is a good moment for some inspired guesswork.
In today's deal, South has to guess after West's annoying four-club opening bid and North's here's-hoping-for-the-best takeout double. However, six diamonds cannot be far wrong.
Once there, how should South plan the play after West leads the club king?
Declarer should see 12 top tricks: three spades, one heart, seven diamonds and one club. But assuming West has an eight-card suit for his four-club opening, South knows that East is void. This means that declarer must play a low club from the board at trick one. And do it again at trick two if necessary.
Note that playing the club ace costs the contract. East ruffs, and South has an unavoidable heart loser.