Dentist coup considered, abandoned, defense slips

A club was led to RHO's Ace, I held off the second, won the third. Next, I attacked spades, jclar (LHO) ducked two rounds of spades. Before leading a third, I had to place LHO with 4234, in that case, I can reach dummy for the heart finesse by "extracting" LHO of all safe exits (by playing D AKQ to remove all of west's diamonds), LHO is welcome to cash a club making three clubs and a spade for the defense, but has to play a major suit for entry to take the heart finesse.

After figuring this out, I cashed two diamonds, and "chickened out" from cashing the third, lest I should be setting up an extra undertrick instead of assuring the contract. Both defenders were following up the line in diamonds! Thus LHO could have beaten the contract with a D exit when in with the third round of spades. But she didnt, I took the H finesse and had nine tricks for 5 IMPS.