One of the world's greatest authorities on the Middle Ages, Professor Robert Bartlett of St Andrew's University, investigates the intellectual landscape of the medieval world. In the first programme, Knowledge, he explores the way medieval man understood the world - as a place of mystery, even enchantment. The world was a book written by God. But as the Middle Ages grew to a close, it became a place to be mastered, even exploited. In Sex, he unearths remarkable evidence of the complex passions of medieval men and women. The Church preached hatred of the flesh, promoted the cult of virginity and condemned woman as the sinful heir to Eve. Yet this was the era that gave birth to the idea of romantic, or 'courtly' love. In Belief, the supernatural comes under the spotlight. The medieval dead shared the world with the living: the cult of the saints, encounters with the dead, and visions of the next world were all seen as proof of a two-way traffic between this world and the next. In the final programme, Power, Professor Bartlett lays bare the brutal framework of the medieval class system. Inequality was a part of the natural order: the life of serfs was little better than those of animals, while the knight's code of chivalry was based more on caste solidarity than morality. The class you were born into determined who you were.