West leads the diamond jack against four spades, won in dummy. Declarer happily plays a spade to the ace, expecting to claim moments later, but West shocks him by discarding. Now declarer is staring down the barrel of defeat unless he can reach dummy to take the marked spade finesse.
In an attempt to steal an entry, he tries the heart four from hand, but West anticipates this tactic — it is suspicious that declarer has suddenly stopped drawing trumps — and goes in with the ace before continuing diamonds. Declarer ruffs, cashes the heart king and then continues his pursuit of a dummy entry by advancing the club queen. This time, both defenders must duck to ensure that declarer is not allowed to force access to dummy on the second or third round of clubs.
The defenders can subsequently arrange to take their club honors and force South with a diamond, leaving declarer to tackle trumps from his hand and concede the setting trick to East’s jack.
Say declarer tries the heart king at trick three instead. Now, in a reverse of the earlier situation, West must duck that. He wins the next heart trick and continues diamonds, resulting in the same position. A low club to the jack is taken by East for a third diamond lead, and then West must play the club king on South’s club nine and lead a fourth diamond.
The reason for flying in here is to deny declarer an entry. Defenders who get this right can pat themselves on the back.