Counter-Intuitive I

West plays in 6NT against North's lead of the ♥10.

Declarer cashes three top hearts and two top diamonds.  South discards on the third heart and also on the second diamond.  Declarer now claims twelve tricks.  How?

Firstly, a disclaimer is in order.  A more competent declarer, focusing not on thirteen tricks but just twelve, would automatically have ducked a club at trick two, thereby enabling the contract to be fulfilled whenever possible.  Subsequently, playing off the top hearts, the ace of clubs, then the spade winners would have effected a simple red-suit squeeze against north on the actual deal.

It so happens, however, that the greedy line of play to this juncture need not be fatal.  Declarer cashes the ace of clubs and the remaining two top diamonds, discarding clubs.  If north shows out on the first club, he is immediately squeezed in three suits.  If north follows to the club lead, then declarer plays three rounds of spades.  If north follows to three spades, then he must be 3-4-5-1; the spade jack is overtaken, and dummy's fourth spade is cashed.

If north shows out on the second or third spade, any discards must be in clubs, lest he set up a red-suit winner.  Unless south has unguarded spades along the way, the spade jack wins; then, south is thrown in with a club to lead a spade to dummy at the end.