How do I make my idea into a movie?

Last night I woke up in a cold sweat because of a terrible nightmare. It took me 10 minutes to wake my fiance up and even with his attempt to cuddle me, I couldn't get the images out of my head. The only weird thing was that the images were original...so was the story. I recently got some bad news and I think that my subconscious was going crazy last night. Anyway, the idea is really original (which is uncommon these days) and I think it would make an amazing thriller (like The Bone Collector) or even good hour long episode of Law and Order (SVU of course ;)). However, I have no idea what do to now. I can't write a screen play, I am a law student - I don't even have time to shower. I don't want to tell anyone about it (because they will steal it) and I don't want to get suckered into a scam (like those get rich quick websites where you tell them your idea and they supposedly pitch it for you). What should I do?