Trust partner's card and south's bidding

[Photo provided to China Daily]

George Eliot wrote, "There are men whose presence infuses trust and reverence."

If your bridge partner is one of those, lucky you. But regardless, you must be able to rely on your partner's bids and plays. Trusting the opponents is a tad more dangerous because they might intentionally be trying to mislead you; however, most of the time, they are dependable.

This deal was played at Bridge Base Online last month. It looks so easy to defeat three no-trump, but it made seven times and failed only thrice. Why?

As a secondary issue, what is the best contract for North-South, and how do they get there?

After West led the spade seven, almost every East won with the ace and returned the spade two, low from three remaining cards. (Two Easts sensibly led back the spade queen, which worked perfectly.)

At every table where the contract made, West took the second trick with his jack and cashed the spade king, under which East failed to unblock the queen.

One East realized that throwing away the queen was safe. If South had started with four spades, he would have responded one spade, not one no-trump.

Each West should have used that same deduction and, at trick three, led the spade six. East would have overtaken with the queen and continued with the three.

The best North-South contract is four hearts, which here would have made easily. But I do not see an obvious way to get there.