Ancient Greece's most powerful god wages an epic struggle against his father for control of the universe. It's the ultimate Clash of the Gods as the Olympians challenge the Titans in mythology's greatest showdown. This is a pivotal battle that experts believe may have been ancient code for a real world event - one of the greatest natural disasters the Earth ever experienced.

In the fourth episode, Morgan Freeman examines how different faiths see the creation of the world, taking him on a journey to the Vatican, Cairo and the jungles of Guatemala.

From director Amy Berg: 'Just a year and a half ago, after spending over four years on the same story for CNN and CBS before that, a paedophile priest named Oliver O'Grady decided he would participate in the film I wanted to make. It became Deliver Us From Evil -- the story from inside the sickest mind possible, the secrets that were meant to stay in the private files and crypts of the Roman Catholic Church, and the blind trust in those they perceived as God's messengers that left families with no faith and children with no innocence. After filming for a week and a half, the then defrocked priest mentioned he might need to move to Canada after this film comes public. Seeing the pain, corruption and missed opportunities to provide ministry to those in need was truly a tragic story to watch and the loss was more devastating than I ever imagined. It was so difficult to be so close to such a horror story that in the priest's words "never should have happened.".

Dr Francesca Stavrakopoulou asks whether the ancient Israelites believed in one God as the Bible claims. She puts the Bible text under the microscope, examining what the original Hebrew said, and explores archaeological sites in Syria and the Sinai which are shedding new light on the beliefs of the people of the Bible. Was the God of Abraham unique? Were the ancient Israelites polytheists? And is it all possible that God had another half?

The world waits as Koresh makes new promise of surrender but the FBI's controversial tactics turn the compound into an apocalyptic scene. U.S. Attorney General Janet Reno approved recommendations of FBI officials to proceed with a final advance in which the Branch Davidians would be removed from the Mount Carmel Center by force.
In an attempt to flush Koresh out of the stronghold, the FBI resorted to pumping CS gas into the compound with the aid of an M728 Combat Engineer Vehicle, which was equipped with a battering ram. In the course of the advance, the Mount Carmel Center caught fire under circumstances that remain disputed. Barricaded inside the building, 79 Branch Davidians perished in the ensuing blaze; 21 of these victims were children under the age of 16. Koresh, then 33, died of a gunshot wound to the head during the course of the fire. It is unknown whether he committed suicide or if he was killed.

Diarmaid MacCulloch's own life story makes him a symbol of a distinctive feature about Western Christianity - scepticism, a tendency to doubt which has transformed both Western culture and Christianity. In the final programme in the series, he asks where that change came from. He challenges the simplistic notion that faith in Christianity has steadily ebbed away before the relentless advance of science, reason and progress, and shows instead how the tide of faith perversely flows back in. Despite the attacks of Newton, Voltaire, the French Revolutionaries and Darwin, Christianity has shown a remarkable resilience. The greatest damage to Christianity was actually inflicted to its moral credibility by the two great wars of the 20th century and by its entanglement with Fascism and Nazism. And yet it is during crisis that the Church has rediscovered deep and enduring truths about itself, which may even be a clue to its future.