As the crash of 1929 plunged the world economy into turmoil, two men emerged with competing claims on how to restore balance. John Maynard Keynes, the mercurial Cambridge economist, believed that government had a duty to spend. He met his opposite in a little-known Austrian economics professor, Friedrich Hayek, who considered attempts to intervene pointless and potentially dangerous. From their first face-to-face encounter to the heated arguments between their ardent disciples, Nicholas Wapshott unearths the contemporary relevance of Keynes and Hayek, as present-day arguments over the virtues of the free market and government intervention rage with the same ferocity as they did in the 1930s.