The loser can be hard to foresee

Henri Poincare, a French polymath who died in 1912, said, "It is far better to foresee even without certainty than not to foresee at all."

That is also true at the bridge table. Better, though, is when declarer can foresee exactly how to make his contract. In this deal, the right line is tough to spot.

How should South plan the play in four spades after West leads a trump?