Thirty years ago, in the centre of China's communist capital, millions of students and citizens staged weeks of protests calling for democracy.The students and their fellow protesters stared down their government in the full gaze of the world's media, demanding an end to totalitarian rule.Then, the People's Liberation Army turned its guns, and its tanks, on its own people.Three decades on, Four Corners vividly brings the story of these momentous times to life, drawing upon a trove of vision and audio captured by ABC reporters and crews in that astonishing spring of 1989.