The U.S.S.R. He was an old man with a seamed face and the compact, hardened body of a laborer, and we met him in a chance encounter at a hallowed place - the immense, brooding scupture marking the spot where more than a 100,000 Jews and Ukrainians were slaughtered at Babi Yar.

I had been here before to do an article and came back recently solely to accompany a fellow correspondent who didn't know the way. I had no thought of doing another piece until the man began telling us a tale of terror and death, safety in false identities and flight across war-torn Eastern Europe.

His hands carving and chopping the nightime air, we listened spellbound to the words of a man who had been an eyewitness to the execution at Babi Yar. It was a story that haunts the imagination.

The man - we will call him Sergei because he feared reprisals even now - was a 24-year old machinist when the Germans swept through the Ukraine and took Kiev in the fall of 1941. He and his family - parents and several siblings - lived in a small town south of Kiev.

"My boss was a Ukrainian, and when the Germans came, he became the collaborationist head of the village Soviet. The Nazies used him. He liked me and wanted to help me. Jews wre being rounded up and I am a Jew. So he gave me false identification papers with a Ukrainian name, and I was safe."

The same was not true for Sergei's family. They were executed by the Germans within a few weeks and buried with others in a mass grave near the village. Sergei went to Kiev where his aunt and uncle and their family lived. But soon, the aunt and uncle, unprotected by any false identification papers, were rounded up and herded, with many thousands of others, into the "lager," prison camp, at the head of the ravine at Babi Yar.

THE OLD MAN pointed out the area where the lager had been, now a series of newly built apartment blocks. "Here is where the Jews were made to take off their clothes," he said, sweeping his hand across the small parking area. "Then they were marched to the ravine."

He pointed off toward the brooding sculpture, which sits on a huge pedestal within the present, landscaped remnant of the ravine.

He told of hearing the cries and screams of anguish and the rattle of machinegun fire as the victims were killed. He fled the area, and soon was seized by the Germans who mistook him for a Ukrainian. He was sent to Germany to work as a slave laborer in a munitions factory.

He spent a year and a half there and then escaped, making his way back eastward to home. He arrived in 1943, about the time the Soviet army finally was dislodging the Wermacht from Kiev.

The collaborationist village chief was executed by the Red Army. Sergei found a job and learned more of what had happened to others.

HE RECOUNTED hearing of how the Germans crowded 7,000 Jews into a mineshaft in Poltava, then sealed them in to die. "It was horrible, a terrible death," he said, his eyes glowing with tears.

After the war, Sergei married and raised a family of his own - a daughter and son - who in the past few years have themselves emigrated to Israel.

And the Germans remain fascists, he believes, unreformed from their wartime days. He visits Babi Yar frequently. "My aunt and uncle are here and others as well. I'm sure," he said.

The night was cold, with a heavy freezing rain sweeping the memorial and clouding the banks of lights that illuminate it.

As we spoke, an old woman with a solitary flower slowly walked up the rough concrete ramp to the foot of the bronze mounment and tucked the stem into a crevice. Then she got down on her knees in the rain and her body shook with tears.

Jew, Ukrainian, Russian . . . no way to tell. Another survivor surely, wracked with memories, come to bear witness on ground sanctified by ghastly sacrifice.