Charles Darwin's own diaries and field notes serve as the spine of this account of the voyage that produced the theory of evolution. The film follows his path as a young naturalist aboard the Beagle, with footage shot at the actual locations he recorded, including the Galapagos Islands, where finch and tortoise variations first pushed him toward his theory. Historians and science commentators appear throughout to place his notebook entries in context, explaining how a private, tentative idea grew into a published argument that upended Victorian science and religion alike. The film also addresses the lasting controversy around his conclusions, treating Darwin as a working scientist assembling evidence over years rather than a man struck by sudden insight. It stays close to the written record he left behind, using his own words to trace how observation became theory.