Contract bridge: analysis of play to first trick reveals position of opponents’ high cards

If you can bid and make 3NT contracts, you will be a bridge winner. Can you see a way to guarantee your contract here?

Bidding
Dealer: South
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West led 7♠ to East’s 10♠ and declarer won the trick with J♠. Needing an extra trick, South attacked the promising-looking club suit, leading Q♣ and, when West followed small, ran it to East’s K♣. But, now, 8♠ was returned, and West took five further spade tricks. Two down in quick time.

Declarer must analyse the play to first trick and visualise the layout of the suit. If East had held A♠ or Q♠, she would have played it. When she contributes only 10♠, this marks West with ♠AQ. Therefore, it is East whom South must keep off lead, for fear of her returning a spade and the frail ♠K5 holding being gobbled up by West. If West gains the lead in another suit, she cannot lead a spade without providing another trick for South.

Since declarer requires only one extra trick, she can obtain it, completely safely, in hearts. At trick 2, she plays 2♦ to A♦, and then leads 3♥. When East plays low, she puts in 10♥. If this wins, that is her ninth trick. In fact, West takes Q♥, and maybe tries 7♣. Declarer must rise with A♣, play a heart to A♥, and then return to dummy with K♦ to cash 10♥ — this is now her ninth trick and her contract secured.