AI tool for assisting with plotting a story?

I need an AI that can help me make some narrative choices about a story I want to write. I have a few places where I have several options for what happens, and can't decide.

I also need it to help me come up with some like specifics for certain things that need to happen. For example one character in the story gets broken up with really cruelly, and I need to figure out what exactly the ex did that was so bad the rest of the story won't seem like an overreaction.