Image upload script not putting src in?

Hello all! I'm trying to integrate CKEditor image upload. I've managed to write a script that will verify that the file came from CKEditor, and upload it successfully to the server. However, once it uploads, my instance of CKEditor simply gets a broken image link.

It gives me something like this:

<p>
<img alt="" />
</p>

Is my upload script supposed to return a path or something?

Thanks for any help.

Josh.