Movies and TV series increasingly feature leading characters that are morally repugnant, and yet we respond positively to their charisma. Why do we like them so much on screen? And is our emotional investment in their stories indicative of moral failure on our own part? This week we're exploring ideas of moral beauty, moral ugliness, and the strange ways in which artists - even in apparently morally neutral fields like architecture - can play with our notions of good and evil.