Mastermind. Opinions plz!!!

Alright, so I'm writing a book called "Mastermind." which I hope to quickly turn into a movie. It's about an orphaned teen girl who belongs and works for the ETD: The Elite Thievery Division. That organization has been at work at thievery for centuries, since the Medieval days. She acts like a thief for her "partners-in-crime", but always returns stolen goods like her father before her. Her goal: To survive under the harsh environment of the ETD, while at the same time, trying to discover the truth of her past, since no one will tell her anything and her ancestor's book had mysteriously gone missing years before. She suspects that there is a lot more in her life than what she's got. I'll have a "Trailer" up soon for a movie I hope. Havent really finished the book yet, though. Does it sound like a good movie/book idea and something I should continue with? Suggestions? Thanks! 
