On June 5, 1989, one day after Chinese troops expelled thousands of demonstrators from Tiananmen Square in Beijing, a solitary, unarmed protester stood his ground before a column of tanks advancing down the Avenue of Eternal Peace. Captured by Western photographers watching nearby, this extraordinary confrontation became an icon of the fight for freedom around the world. FRONTLINE investigates the mystery of the tank man — his identity, his fate, and his significance for the Chinese leadership.