Is there a theme in In Cold Blood?

I have
suggested elsewhere that one important theme in's book is the way two young men may be
relatively harmless when they are separate but can make a lethal combination when they get
together. They are like two chemicals that are innocuous in separate bottles but can create an
explosion when mixed together. Dick Hickock and Perry Smith are small-time delinquents who are
both trying to impress each other with how BAD they can be. Neither one of them would have
committed such a horrendous crime by himself, but when they get together they goad each other
into doing terrible things...