Love is a universal and powerful emotion, but it can also be destructive. Lust can destroy; betrayal can wound. Such often-irrational forces ask questions of any society. This episode tells the medieval romance of Tristan and Isolde, whose love affair threatened the fate of their kingdom. We explore how the abandonment of Dido by the hero Aeneas paved the way for Rome. We see how Norse attitudes to sex and marriage were expressed in the burlesque farce the Lay of Thrym. And, we meet Medea, guilty of the darkest crime of love and passion - the murder of her own children.