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.

Professor Robert Bartlett explores the impact of the Normans on southern Europe and the Middle East. The Normans spread south in the 11th century, winning control of southern Italy and the island of Sicily. There they created their most prosperous kingdom, where Christianity and Islam co-existed in relative harmony and mutual tolerance. It became a great centre of medieval culture and learning. But events in the Middle East provoked the more aggressive side of the Norman character. In 1095, the Normans enthusiastically answered the Pope's call for holy war against Islam and joined the first crusade. They lay siege to Jerusalem and eventually helped win back the holy city from the muslims. This bloody conquest left a deep rift between Christianity and Islam which is still being felt to this day.

Travelling from the unique Muslim contribution in the medieval south, Andrew Graham-Dixon immerses himself in true Spanish culture and meets the people who live and work with this artistic legacy. He looks at Muslim political and cultural influence as he travels from Cordoba to Granada, seeing classic buildings such as the Great Mosque in Cordoba, the Alcazar in Seville and the Alhambra in Granada. He also shows how the Moors introduced new foods – including citrus fruits, coffee and spices

Political humorist and author Bill Maher travels around the globe interviewing people about God and religion. Known for his analytical skills, wit and commitment to never pulling a punch, Maher brings his characteristic honesty to an unusual spiritual journey.
Muslims, Jews and Christians of many kinds pass before his jaundiced eye. He goes to a Creationist Museum in Kentucky, which shows that dinosaurs and people lived at the same time 5000 years ago. Maher speaks to a rabbi in league with Holocaust deniers. He talks to a Muslim musician who preaches hatred of Jews. Maher finds the unlikeliest of believers and, in a certain Vatican priest, he even finds an unlikely skeptic.

Michael Wood charts the coming of Islam to the subcontinent and one of the greatest ages of world civilisation: the Mughals. He visits Sufi shrines in Old Delhi, desert fortresses in Rajasthan and the cities of Lahore and Agra, where he offers a new theory on the design of the Taj Mahal. He also looks at the life of Akbar, a Muslim emperor who decreed that no one religion could hold the ultimate truth, but whose dream of unity ended in civil war.

The Queen of Sheba - an exotic and mysterious woman of power - is immortalised in the world's great religious works, among them the Hebrew Bible and the Muslim Koran. She also appears in Turkish and Persian painting, in Kabbalistic treatises, and in medieval Christian mystical works, where she is viewed as the embodiment of Divine Wisdom and a foreteller of the cult of the Holy Cross. In Africa and Arabia her tale is still told to this day and, indeed, her tale has been told and retold in many lands for nearly 3,000 years.