There is the main theme of trust. We have to know whom we can trust, our lives may depend on it. We can always trust Jesus. The novel is written around the underground railroad that helped slaves escape to the North. It was definitely life threatening to know who to trust.
The novel is a microcosm for a macrocosm as the reader follows Daisy, a young slave. We see her bravery and tenacity and her capacity to care for others.