That I thought. Your plan is right, coz 2S opener couldn't have probably DK - finesse not going. So need to ruff 2 spades in dummy, but you have not entries into hand. Only way - H10 in North's hand (or singleton 10 falling from South on 1st draw). Even if North having 10xxx in hearts, then y may win, if he has 3+ clubs and DK is onside. On tournament, this board played on 30 tables - 9 times 6H down 1; 2 times 6H down 2; once 6H down 3; 6 times 4H +1 trick; 1 time 4H just made ( other contracts: 4 times 6C down 2; once 6NTx down 1; once 5C down 1; once 3NT +1 trick; once 4C just made; 3 times NS-line played spades)... Interesting, that no one declarer playing Hearts, couldn't manage to take 12 tricks!