Bettany investigates the revolutionary ideas of Karl Marx. Born to an affluent Prussian family, Marx became an angry, idealistic radical, constantly on the run for his political agitating and incendiary writing.

The philosopher Friedrich Nietzsche was one of the most brilliant and dangerous minds of the 19th century. His uncompromising and often brutal ideas smashed the comfortable presuppositions and assumptions of religion, morality and science.

Historian Bettany Hughes travels to Vienna on the trail of Sigmund Freud - the father of psychoanalysis. Freud's influence surrounds us. In our vocabulary: repression, the Freud slip, and in the freedom we take for granted, to talk openly about our deepest feelings and insecurities. A pioneer in the study of the human mind, Freud's psychoanalytic methods addressed emotional issues, seldom even discussed in the 19th-century.