If this split, that; if that split, this

Richard Dooling, a novelist and screenwriter, said, "Making money, it seems, is all about the velocity of moving it around, so that it can exist in Hong Kong one moment and Wall Street a split second later."

This deal has a split personality. If there is one particular split, declarer adopts line A; but if there is a different split, he follows line B. What are those splits and lines? Take several split seconds.

South is in four hearts. West cashes his three top diamonds, then shifts to the club 10, which is won by declarer's ace.