Source: Wikipedia

Morton’s Fork is a coup in contract bridge that forces an opponent to choose between:

  1. letting declarer establish extra tricks in the suit led; or
  2. losing the opportunity to win any trick in the suit led.

It takes its name from the expression Morton’s Fork.

It appears that South has both a heart and a club loser. Although South can establish another winner in diamonds, just one discard on a diamond honor doesn’t help.

K Q 9 8
K 9 8
K Q 9
K 9 8
3
A 10 5 3
J 10 7 3 2
J 5 4
2
J 6 4 2
A 8 6 5 4
Q 3 2
A J 10 7 6 5 4
Q 7

A 10 7 6

South is in 6 Spades

Opening lead:J

South receives the lead of theJ against 6. However, there are two ways that the contract can be made. South might manage to avoid any heart loser. Or, South might take two heart tricks; in that case, South could discard one club on theK and another club on a diamond honor.

Judging from the opening lead that East holds theA, South plays the9 from dummy at the first trick, ruffs in hand, and draws trumps. Hoping that West holds theA, South leads the7, executing Morton’s Fork:

  • If West takes theA, declarer can win any return, unblock hearts, take a ruffing finesse against the ace of diamonds, then discard two clubs on dummy’s winning diamond andK. In this case South loses only a heart.
  • If West ducks South’s lead of the7, declarer wins dummy’sK, takes a ruffing finesse against the ace of diamonds, and throws theQ on the established diamond winner. In this case South loses only a club.

Note that declarer must be careful not to play a high diamond on the opening lead, as East could then withhold the ace. That would force the declarer to choose a discard prematurely. South must get a discard on a diamond honor eventually, but not before West has been forced to decide whether to take theA or duck it. Only then will South know whether to discard a heart or a club on the diamond winner.