I got this question recently:
“I love to have a twisted ending. I want the reader/audience to sit at the end of the movie/screenplay with mouth on the floor, and say, Oh, that was a badass ending. What is the best way to include this in the query letter without making it a dead give away? Or do you want it to be a dead give away?”
I’ve gotten this question a few times. I don’t think there is a right answer to this question. The main thing you want to do, at all costs, is get people to read your script, so if that means giving away the ending in your query letter then that’s what you have to do. If you can write a compelling query letter without giving away the ending, then great, but if by giving away the ending you feel like your query letter is better and you will get more requests for the full script, then that’s what you must do.