What had she done? Her family was deeply suspect, of course. Her father, Werner, was a capitalist, with a factory that the East German government could not touch because it was in West Berlin. Her mother, Carla, was a well-known Social Democrat. Her grandmother, Maud, was the sister of an English earl.

However, the authorities had not bothered the family for a couple of years, and Rebecca had imagined that her marriage to an official in the Justice Ministry might have gained them a ticket of respectability. Obviously not.

Had she committed any crimes? She owned a copy of George Orwell’s anti-Communist allegory Animal Farm, which was illegal. Her kid brother, Walli, who was fifteen, played the guitar and sang American protest songs such as “This Land Is Your Land.” Rebecca sometimes went to West Berlin to see exhibitions of abstract painting. Communists were as conservative about art as Victorian matrons.

Washing her hands, she glanced in the mirror. She did not look scared. She had a straight nose and a strong chin and intense brown eyes. Her unruly dark hair was sharply pulled back. She was tall and statuesque, and some people found her intimidating. She could face a classroom full of boisterous eighteen-year-olds and silence them with a word.

But she was scared. What frightened her was the knowledge that the Stasi could do anything. There were no real restraints on them: complaining about them was a crime in itself. And that reminded her of the Red Army at the end of the war. The Soviet soldiers had been free to rob, rape, and murder Germans, and they had used their freedom in an orgy of unspeakable barbarism.

Rebecca’s last class of the day was on the construction of the passive voice in Russian grammar, and it was a shambles, easily the worst lesson she had given since she qualified as a teacher. The pupils could not fail to know that something was wrong and, touchingly, they gave her an easy ride, even making helpful suggestions when she found herself lost for the right word. With their indulgence she got through it.

When school ended, Bernd was closeted in the head’s office with officials from the Education Ministry, presumably discussing how to keep the school open with half the staff gone. Rebecca did not want to go to Stasi headquarters without telling anyone, just in case they decided to keep her there, so she wrote him a note telling him of the summons.

Then she caught a bus through the wet streets to Normannen Strasse in the suburb of Lichtenberg.

The Stasi headquarters there was an ugly new office block. It was not finished, and there were bulldozers in the car park and scaffolding at one end. It showed a grim face in the rain, and would not look much more cheerful in sunshine.

When she went through the door she wondered if she would ever come out.

She crossed the vast atrium, presented her letter at a reception desk, and was escorted upstairs in an elevator. Her fear rose with the lift. She emerged into a corridor painted a nightmarish shade of mustard yellow. She was shown into a small bare room with a plastic-topped table and two uncomfortable chairs made of metal tubing. There was a pungent smell of paint. Her escort left.