If you adapt an adaptation do you still have to pay royalties?

Question

For example, a lot of people adapt Dickens A Christmas Carol. So it would be like taking someone's adaptation of A Christmas Carol and adapting it. Is there anywhere I could check this out?

Answer 1

I assume Dickens is public domain, so if you adapted from him, you would not need to pay royalties, but if you adapt from a copyrighted adaptation that has royalty, you are probably breaking the copyright law, but then how is anyone going to tell what your original source was?

Answer 2

Actually I know a guy who did an adaptation of A Christmas Carol. I'll email him and get back to you.