So I want to write a kind of cop story thing. The one thing I'm having trouble with is the main character (Sam, short for Samantha) is a cop. She was super super idealistic and wants to catch every single criminal in the entire world. There was this one burglar, a kind of literal cat burglar (she can turn into a cat), who the cop just chased obsessively. Then there was of course the kind of hilarious hijinks and amusing antidotes with the burglar getting away some way or another. (in the style of Lupin the 3rd, Man of Many Faces)
But then something happens, something that makes the cop doubt the entire system, lose the ideals, and basically become really disillusioned. I just don't know what that something is.
Help?