You hold, in first seat with neither side vulnerable:
You pass. LHO opens 1 Spade. Partner overcalls 2 Hearts, and RHO passes. What would you bid?
You have great trump support, a void in the opponents' suit, and 7 losers overall. As partner's bid promises opening bid values, you surely want to be in game. You could just bid 4 Hearts. But since you want to be in game, you have a chance to show partner what you have along the way - a splinter bid of 3 Spades. Since you are a passed hand, partner won't expect more than this. If you bid 3 Spades, its effect is magical. Now put yourself in partner's chair. He holds
Surely partner has the ace of hearts. She has at most one spade. So your only losers are two spades and two diamonds. The hand is worth a slam try, so you cue bid 4 Clubs. Partner responds with a cue bid of 4 Diamonds, which has to be the king. Now I think there is enough information to just go ahead and bid 6 Hearts. However, if you want to really be on the safe side, you can bid 4NT, RKC for hearts.
Now go back and look at that first hand. You would like to show the void. However, the way to show a void with one keycard is usually to jump to the 6-level in the void suit. Here, you would have to bid 6 Spades, which is higher than slam in your suit. What many experts do in this situation is to jump to 6 of the trump suit, showing one keycard and a void in a higher-ranking suit. You could do this, or, to be on the safe side, just show one keycard. I would show the void, since this may be what partner needs for a grand slam. Whatever you do, partner will put it into 6 Hearts.
It is quite possible that a 3 Spade splinter bid will encourage LHO, holding
to compete with 4 Spades. But partner would cue bid 5 Clubs and the slam would still be reached. Now you will be either +980 or +500 if the opponents save in 6 Spades.
Looking at the two hands together,
you see that 12 tricks are easy (just ruff all the spades in dummy), and 13 are possible if you can ruff out the club suit and set up dummy's long club. Dummy has plenty of entries to do this.
What actually happened was that we lost the battle but won the war. My partner (not Jenn) missed the opportunity to make the splinter bid, bidding 4 Hearts to end the auction. However, things turned out good for us anyway. Nobody in the field (it was bid 9 times) got to the slam. Clubs were 5-2, so the hand should only make six, but at our table, our opponents misdiscarded and I ended up making 3 diamond tricks for +510, a top on the board. Fortunately this was a pairs game. If it had been teams, it would have been a lost opportunity to win 11 IMPs.