Premise, What is your story about?

I have read my how to write books, searched the Internet for premise. It finally dawned on me how to write my one sentence of what my story is about. Maybe what I have realized will help you.

I tried to write my premise from the inciting incident which is at the beginning of the book or the opening conflict. The inciting incident is what happens to cause events leading up to the protagonist's point of no return. The point of no return is what happens ¼ of the way through the novel that changes everything the hero knows. This is where the story begins. The first ¼ of your book is bringing all of the characters together. It is the normal for your character even if the character’s life changes in some way.

Your one line summary would be:

When (point of no return happens) protagonist must do something to stop antagonist or what’s at stake will happen or won’t.

Now I’m trying to figure out through lines, but that will be another post.