Her mother was in tears. “We will see you,” she said. “You can fly to West Berlin any time you want, and we can just walk across the border and meet you. We’ll have picnics on the beach at the Wannsee.”

Rebecca was trying not to cry. She put the money in a small shoulder bag that was all she was taking. Anything more in the way of luggage might get her arrested by the Vopos at the border. She wanted to linger, but she was afraid she might lose her nerve altogether. She kissed and hugged each of them: Grandmother Maud; her adoptive father, Werner; her adoptive brother and sister, Lili and Walli; and last of all Carla, the woman who had saved her life, the mother who was not her mother, and was for that reason even the more precious.

Then, her eyes full of tears, she left the house.

It was a bright summer morning, the sky blue and cloudless. She tried to feel optimistic: she was beginning a new life, away from the grim repression of a Communist regime. And she would see her family again, one way or another.

She walked briskly, threading through the streets of the old city center. She passed the sprawling campus of the Charité hospital and turned on to Invaliden Strasse. To her left was the Sandkrug Bridge, which carried traffic over the Berlin-Spandau Ship Canal to West Berlin.

Except that today it did not.

At first Rebecca was not sure what she was looking at. There was a line of cars that stopped short of the bridge. Beyond the cars, a crowd of people stood looking at something. Perhaps there had been a crash on the bridge. But to her right, in the Platz vor dem Neuen Tor, twenty or thirty East German soldiers stood around doing nothing. Behind them were two Soviet tanks.

It was puzzling and frightening.

She pushed through the crowd. Now she could see the problem. A crude barbed-wire fence had been erected across the near end of the bridge. A small gap in the fence was manned by police who seemed to be refusing to let anyone through.

Rebecca was tempted to ask what was going on, but she did not want to draw attention to herself. She was not far from Friedrich Strasse Station: from there she could go by subway directly to Marienfelde.

She turned south, walking faster now, and took a zigzag course around a series of university buildings to the station.

There was something wrong here, too.

Several dozen people were crowded around the entrance. Rebecca fought her way to the front and read a notice pasted to the wall that said only what was obvious: the station was closed. At the top of the steps, a line of police with guns formed a barrier. No one was being admitted to the platforms.

Rebecca began to be fearful. Perhaps it was a coincidence that the first two crossing places she had chosen were blocked. And perhaps not.