When you see the Spade king on the table you know there is no point in encouraging or discouraging at trick One.

You need to tell partner what to play next and you will do this wih a SUIT PREFERENCE signal. So on partner's lead drop the ♥10 on the lead asking partner to immediately switch to Hearts as you are sitting over dummy with your Ace Jack and maybe partner has the Queen

Partner does indeed switch toe the ♥Q and you now proceed to take the first 3 tricks with a successful finesse for the defenders against dummy's ♥King

Had partner switched to Clubs then this will be part what I call the FREE GIFTS DEPARTMENT in giving away a free finesse to declarer and allowing him to make up to 11 tricks.

(NB with neither North nor South attesting to bid No Trumps a Spade lead is called for) Perhaps North with the KJ of Spades might have tried 3NT instead of 3♥.