After West opens and rebids , South gets to declare 4.
West kicks off with the Ace of and switches to the Ten of . On first sight there doesn’t seem any trouble at the horizon, you can afford to lose a trump and two . But if that is a singleton and the trumps break 4-1, your halcyon days in paradise are about to be disturbed.
At the table the Jack of won the trick and so did the Ten of . Without a sign of worry you play dummy’s other trump, but East shows out. West reveals his evil plot when he cashes the King of before exiting with a to dummy.
So West is 6-4 in the pointy suits, and the promotion of the 9 cannot be prevented anymore if that actually was a singleton…
The antidote to that fatal trump promotion is … liberating. You need to extract West’s exit cards before continuing drawing trumps. So go back in time for a moment and right after you ran the Ten cash the Ace & King. Now you can continue trumps and West can win anytime he wants but is left toothless. Forced to play you can wrap up your ten tricks.
Unscathed you can enjoy the warm sun on your face again.