Characters
We're not just an uncle and a niece. It's something else. I know you. I know you don't tell people a lot of things. I don't either. I have a feeling that inside you there's something nobody knows about... something secret and wonderful. I'll find it out.
— Young Charlie

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
Charlie says their bond with the uncle goes beyond family labels. Both keep things to themselves, and Charlie senses something secret and wonderful hidden inside. It's a confident promise to find out what it is.
Context reviewed