What is the theme in The Silence of the Lambs by Thomas Harris?

Ambition is Clarice Starling's driving motivation. Starling is proud of her father and mother, and so she never speaks ill of her indigent upbringing. However, the reader learns, through Starling's reactions to the poverty of Frederica Bimmel, just how much Starling hated growing up poor in the country. As Starling looks at the ancient, dusty rubbish piled up in Frederica's home, she wonders if Frederica had a friend good enough to take through that mess. This thought reveals Starling's buried shame about her own upbringing. Being called a rube or a redneck, even by the likes of Lecter, is her worst nightmare. Her desire to leave that rural poverty behind and become a part of the elite power structure at the FBI is intense.