David Attenborough narrates this account of Charles Darwin, walking the same paths at Down House where Darwin once paced through his ideas and tracing the voyage of HMS Beagle that took a young naturalist to the Galapagos Islands. Attenborough treats Darwin as a personal hero, and the film follows the finches, tortoises, and barnacles that pushed Darwin toward a theory he knew would upset Victorian society and his own religious wife. Archival letters, sketches from Darwin's notebooks, and location filming at the actual sites Darwin visited stand in for reenactment, while Attenborough's own fieldwork, including his encounters with living relatives of the species Darwin studied, ties nineteenth-century observation to modern evolutionary biology. The film also covers Darwin's twenty-year delay in publishing On the Origin of Species, the pressure from Alfred Russel Wallace that finally forced his hand, and the fossil and genetic evidence gathered since that confirms the tree of life Darwin first sketched as a rough diagram in his notebook.