Help Me Out Here?????

Okay, I am currently working on a manga/comic book and I've been struggling to find a good, strong plot line. So far what I've been working with is that there are people called "Dream Catchers" whose goal it is to eliminate "Nightmares", which begin as dreams but feed off terror and are eventually able to grow strong enough to take on the form of a human that will then wreak havoc in the real world, and it's the Dreams Catcher's job to keep them at bay. Please be brutally honest with me, do you think this is a good idea? I really need a second opinion. Also, if possible could you give me some tips for improvement?