Yeah. You hold some rights. For example, you don't get the rights to the characters or setting since they're not original, but you do get the rights to the unique events that happen in your plot.
For example, if you write "Harry Potter Goes to France", Harry Potter is obviously not yours, but the story of going to France is new and original. If you wanted, you could reskin that story with some original wizard kid and be fully in the clear.
Hypothetically, anyway. I'm not sure that this has been tested in court.