JIM LEHRER: Next tonight, 20 years after Tiananmen Square. We have two looks. First, from Beijing today, John Ray of Independent Television News reports.
JOHN RAY: Two decades have passed, but still they cannot mourn their dead in peace. Today, we found that even a cemetery is no sanctuary.
Here lie many of the victims of Tiananmen, but only a handful of relatives are allowed to lay flowers.
And what are your feelings when you come back?
CHINESE WOMAN: It's very difficult to say. I'm saying only in my heart.
JOHN RAY: The heady spring of '89, when a million demanded liberty and democracy, ideals that died on June the 4th amid the rattle of gunfire and the rumble of tanks, a story that still can't be told in the place where it happened.
So Zhang Xian Ling treasures fragments of a secret history, the slogans of a lost rebellion, and a motorcycle helmet with a bullet hole from the shot that killed her son, Wang Nan, just 19 years old.
ZHANG XIAN LING, Tiananmen Mother (through translator): The government killed people. They committed a crime. It's like a murderer at large. They don't want anybody to talk about it.
JOHN RAY: The army never left Tiananmen. Today, security was tighter than ever. China has grown rich, yet its rulers feel insecure.
Surveillance is as tight as I've ever seen it here before. There are army, police, plain-clothed security that far outnumber the tourists. Tiananmen was 20 years ago, but still it apparently terrifies the Chinese communist regime.
WU'ER KAI XI, Tiananmen Student Leader: Extreme anger, seeing a whole floor covered with blood, and the victims pile up.
JOHN RAY: Twenty years ago, this man was number two on China's most-wanted list, the student leader who's lived ever since in exile, but dares still to hope.
WU'ER KAI XI: They want people to forget. They want people to just simply let it go. But the justice needs to be done.
JOHN RAY: But China is a nation forbidden to remember, while a few are unable to forget.