This guy is a moron. If you have a good screenplay or movie idea, you pitch them to producers with a short treatment. Nobody ever buys stories or screenplays without knowing what the idea is first unless the person who came up with it already has several blockbusters under their belt already. And even then, that isn't very common.
I would say this guy either doesn't know that that's what he's supposed to do (in which case, a short google session would have led to a number of articles on how to shop his idea around), or he already has pitched it to a number of producers and not impressed any of them and is hoping to find an idiot to pay him for "Alligators on a Train" or "it's like James Bond, but in SPACE!".