In a double-dummy problem, both sides play with knowledge of all 52 cards. The contract can be made. South leads a club to the king, and ducks the four of diamonds to East. East returns a heart.
South wins and ducks a club to East.
A heart return gives declarer ten tricks by force, so East returns a diamond. South wins and runs clubs, dummy coming down to four spades and the deuce of diamonds. West must come down to a singleton spade, for, if he blanks the diamond king, he can be stripped of spades and thrown in, forced to give South an extra heart trick. Now, if East discards a heart, South cashes his other high heart, discarding a diamond from dummy. South then leads the eight of spades to the ace, and throws East in with a low spade.