What is the underlying message of the book "The Silence of the Lambs"?

The Silence of the Lambs is a complex novel with likely more than one underlying message. It clearly explores the nature of evil, and it has much to say about the lengths people will go to to get what they need or want. 
One of the book's subjects explores how law enforcement personnel must sometimes negotiate with criminals and deal with the obstructive actions of other involved parties in order to solve crimes and prevent other crimes from occurring. Clarice Starling, though very intelligent and intuitive, is intellectually outmatched by the brilliant Hannibal Lecter, a psychiatrist and imprisoned serial killer.  In exchange for information that lends insight on the serial killer Buffalo Bill, Clarice must not only endure the manipulations of Lecter but also overcome the duplicity and jealousy of Chilton, Lecter's jailer and the director of the hospital for the criminally insane where Lecter is held. 
Lecter's ultimate escape is the outcome of Chilton's incompetence and obstruction, but the combination of Lecter's clues and Starling's intelligence enable her to save Buffalo Bill's final victim.