Documentary which tells the story of the theory of evolution by natural selection which is now scientific orthodoxy, but when it was unveiled it caused a storm of controversy. Many people criticised it for being short on evidence and long on assertion and Darwin, being the honest scientist that he was, agreed with them. He entrusted future generations to complete his work and prove the essential truth of his vision. Evolutionary biologist Professor Armand Marie Leroi argues that, with the new science of evolutionary developmental biology (evo devo), it may be possible to take that theory to a new level - to do more than explain what has evolved in the past, and start to predict what might evolve in the future.

In the third part of his journey into the history of Christianity, Professor Diarmaid MacCulloch charts Orthodoxy's extraordinary fight for survival. After its glory days in the eastern Roman Empire, it stood right in the path of Muslim expansion, suffered betrayal by crusading Catholics, was seized by the Russian tsars and faced near-extinction under Soviet communism. MacCulloch visits the greatest collection of early icons in the Sinai desert, a surviving relic of the iconoclastic crisis in Istanbul and Ivan the Terrible's cathedral in Moscow to discover the secret of Orthodoxy's endurance.