This is a problem I encounter sometimes and have recently. My plot has a trajectory to go in a certain direction, but a character needs to do something to make them get to that point. Sometimes it feel sudden, out of character, or just out of place.
Here’s an example. One of my protagonists in a work in progress is an adult who ran away from her cushy background to try the life of a rogue. She meets a scholar and befriends him, but the scholar is working with his order to instigate political tension by way of my main character. Because of their friendship, he eventually betrays his order and tries to help the main character.
(That’s a really poor description, but hopefully you’re still with me.) But why would this guy betray his order? He barely knows the main character at the point this needs to happen, and I didn’t feel “he fell in love” was a good enough reason. I wanted to keep the character a bit enigmatic, but the problem was he was enigmatic to me.
So how do we solve these problems when we encounter them?