When you can see the right line of defense, it behooves you to take charge; partner might not have the same information, after all. If you cannot do the deed yourself, you might have to find a way to remove partner’s losing option, be it via signaling or more drastic measures. That is the theme of this week’s deals.
When returning partner’s suit, the standard method is to give current count — to play back the highest of a remaining doubleton or else your original fourth-highest. Thus, when East wins with the heart ace at trick one against three no-trump, it looks right to play the five back.
However, consider the effect that might have here. When South plays the queen, West could easily look upon East’s heart five as high from 5-3 remaining and duck, to keep a link with his partner and eventually score two further heart tricks. West has no outside entry, after all. (Imagine East has three hearts and K-J-x in clubs as an example of when the duck might be right.)
East should try to persuade West not to duck. The way to do that is to play back the heart three, feigning an original four-card suit. Now West has no reason not to capture South’s heart queen with the king and continue with the 10. East might consider ducking but should not do so — after all, an opening lead from K-10-2 is not a likely choice. The recommended play is necessary to unblock the suit in that it allows East to overtake the heart eight on the fourth round to cash the 13th card.