The bidding often influences the play

Salvador Dali said, "The secret of my influence has always been that it remained secret." It is a secret from some bridge players that the bidding influences the play. They forget the auction when trick one begins.

In this deal, East can find the winning defense if he asks himself what key clue the bidding supplies. West leads the heart nine against four spades. How should East defend?

After North rebid one no-trump, showing a balanced hand with 12-14 points, South plunged into the contract that he hoped he could make.