For the past 12 weeks, the metropolis of Hong Kong - normally one of the world's most vibrant yet orderly cities - has been convulsed by turmoil, as its people rise up against mainland Chinese rule. Pro-democracy protestors have repeatedly seized control of key parts of the city, including its airport. These "flash mob" actions are designed to create maximum chaos and embarrassment for the city's political leadership and their masters in Beijing. It has become an epic battle of wills. On Monday Four Corners goes on the frontline of the protests, capturing the full force of the escalating violence with extraordinary footage.