South won with the king and led the diamond jack.

He led his diamond jack, and East took her winners.

South would then have had to guess the position of the diamond jack to make the slam.

Consider whether South can make six diamonds after the lead of the diamond jack.

Instead he did not reason correctly and led the diamond jack.

He led the diamond jack and thought again when East played low.

He won the opening club lead and ran the diamond jack, losing to the king.

Suddenly, South had to guess who held the diamond jack.

The diamond jack was led to the queen, and he won his king.

The result was down two when the diamond jack did not fall.