Michael Wood's epic series moves on to the revolutionary years after 500BC - the Age of the Buddha. Travelling by rail to the ancient cities of the Ganges plain, by army convoy through northern Iraq and on down the Khyber Pass, he shows how Alexander the Great's invasion of India inspired her first empire. Michael visits India's earliest capital, Patna, and using archaeology, legend and 'India's Rosetta stone', he shows how the ideas of the Buddha - 'India's first and greatest protester' - were turned into political reality by an Indian emperor who sowed the seeds of 'the most dangerous idea in history'.