Charles Darwin, a young man without purpose or career, eagerly agrees to travel the world in the ship, the H.M.S. Beagle. Since he is the only naturalist willing to take the trip, Captain Robert FitzRoy reluctantly welcomes him aboard. The men embark upon their journey and form an uneasy friendship, which is soon challenged by their encounters with slavery in the New World, specifically Brazil. While FitzRoy revels in the benefits of power, Charles struggles to understand his own emerging views on the world. When the two men come into conflict over the treatment of slaves, the future of evolutionary science is at stake.