Assume East has the king

Plan the play in Four Hearts after West leads a low Spade, East’s overcalled suit, East winning the King, cashing the Ace, and leading a third Spade, which you ruff.

* Awkwardly placed, as he cannot make his planned no trump rebid without a stopper in the opposing Spades.

** Showing his delayed support for partner’s known five-card suit, implying a decent doubleton.

*** Prepared to play the five-two fit, given his fine trump quality.

The danger of drawing trumps is that, should they be splitting in their most likely way (four-two), you will have none left. Diamonds must be broached first – but how? West never squeaked, in spite of holding three-card support for his partner’s overcall, so you should be inclined to place the King of Diamonds with East.

Without the danger of a Diamond ruff, your best play would be to cross to the Ace of Diamonds, back to a Heart then lead a second Diamond, covering West’s Knave with the Queen (if it appears) otherwise ducking. However, if West does have Knave-doubleton, East can simply give his partner a third-round ruff.

So, you must guess which is more likely: East with King-low, or King-low-low? Because he has greater Spade length, the former is surely more probable. Therefore, cross to a top Club and lead a low Diamond from dummy. East may well rise with the King from Kinglow, and even mistakenly from King-low-low. But if he boldly plays low (from his actual King-low), win West’s return, draw trumps and lead a Diamond to the Ace. The King is felled and that’s game made.