You need to be very careful. If this were a novel I'd see if I could find a literary agent with a film/TV rights department to take a look at it for me, but with just a short story on the table, I doubt it would be lucrative enough for an agent to consider.
A lawyer is unlikely to be able to help you unless they're a specialist IP lawyer, and even then they'll need specialist knowledge in this area. Do be careful.
Also, are they asking for the rights to the story, or just an option on those rights? There's a big difference.