Savage ask Townsend to become a spy for the Union, telling him he should stand up for his conviction that slavery is wrong. Do you think that's why he ultimately agrees?
Like the term "blockade runner," "spy" has a negative connotation. By agreeing to be a spy, is Townsend exchanging one bad situation for another – the lesser of two evils – or is being a spy truly the more noble course of action?