Say the heart finesse loses. The percentage play for taking 5 spade tricks is to play a spade to the Queen. This play will win whenever West has King and one other spade, or when West has three spades to the King and East has the singleton Jack (in this case you can come back to hand and play a spade to the 10).

Suppose the heart finesse wins. How do you play the spade suit now? If you play a spade to the Queen, and it loses to the King. You win East's return in hand and play another spade towards dummy and West follows with a low spade. You now need to guess whether East started with the singleton King, or King-Jack doubleton. Playing a spade to the 10 initially is no better; if East wins the Jack, you are left with the same guess. Fortunately, there is a safety play to restrict your spade losers to 1 as long as East does not have three or more spades headed by the King and Jack. Lay down the ♠A. If either defender follows with an honor, your problems are solved. If both defenders follow with low cards, you will come back to hand and play a spade towards the Queen. On this hand, proper technique is awarded with an overtrick, as the ♠A fells the King from East. You can now come back to hand and play a spade to the 10, and score all 13 tricks.

Analysis:
A double dummy analysis is not suitable for this deal, as looking at all four hands, it would be trivial (or impossible) to play the spade suit for no losers. The point of the deal is to find the optimal play with only two hands in view.

Bridge Baron's Line of Play
Bridge Baron won the opening lead in hand, and tried to find clues by playing the club Ace and King and a diamond to the King (Baron's play of cashing side suit winners is not desirable, as an enemy ruff could materialize). At this point, Baron took the heart finesse, which won. After seeing the singleton K of spades, Baron made short work of the deal, by playing a spade to the Ace, crossing over to hand with a heart ruff, and playing a spade to the 10 to chalk up the overtrick.
Par Contract Analysis:
The par contract on this deal is 7♠.

Bridge Baron deal No : N2975-71213-92829-77906-78782-23227