It was a miracle there was still a Jewish hospital. Very few Jews were left in Berlin. They had been rounded up in their thousands and sent away in special trains. No one knew where they had gone or what happened to them. There were incredible rumours about extermination camps.

The few Jews still in Berlin could not be treated, if they were sick, by Aryan doctors and nurses. So, by the tangled logic of Nazi racism, the hospital was allowed to remain. It was mainly staffed by Jews and other unfortunate people who did not count as properly Aryan: Slavs from Eastern Europe, people of mixed ancestry, and those married to Jews. But there were not enough nurses, so Carla helped out.

The hospital was harassed constantly by the Gestapo, critically short of supplies, especially drugs, understaffed and almost completely without funds.

Carla was breaking the law as she took the temperature of an eleven-year-old boy whose foot had been crushed in an air raid. It was also a crime for her to smuggle medicines out of her everyday hospital and bring them here. But she wanted to prove, if only to herself, that not everyone had given in to the Nazis.

As she finished her ward round she saw Werner outside the door, in his air force uniform.

For several days he and Carla had lived in fear, wondering whether anyone had survived the bombing of the school and lived to condemn Werner; but it was now clear they had all died, and no one else knew of Macke’s suspicions. They had got away with it, again.

Werner had recovered quickly from his bullet wound.

And they were lovers. Werner had moved into the von Ulrichs’ large, half-empty house, and he slept with Carla every night. Their parents made no objection: everyone felt they could die any day, and people should take what joy they could from a life of hardship and suffering.

But Werner looked more solemn than usual as he waved to Carla through the glass panel in the door to the ward. She beckoned him inside and kissed him. ‘I love you,’ she said. She never tired of saying it.

He was always happy to say: ‘I love you, too.’

‘What are you doing here?’ she said. ‘Did you just want a kiss?’

‘I’ve got bad news. I’ve been posted to the Eastern Front.’

‘Oh, no!’ Tears came to her eyes.

‘It’s really a miracle I’ve avoided it this long. But General Dorn can’t keep me any longer. Half our army consists of old men and schoolboys, and I’m a fit twenty-four-year-old officer.’

She whispered: ‘Please don’t die.’

‘I’ll do my best.’

Still whispering, she said: ‘But what will happen to the network? You know everything. Who else could run it?’

He looked at her without speaking.

She realized what was in his mind. ‘Oh, no – not me!’

‘You’re the best person. Frieda’s a follower, not a leader. You’ve shown the ability to recruit new people and motivate them. You’ve never been in trouble with the police and you have no record of political activity. No one knows the role you played in opposing Aktion T4. As far as the authorities are concerned, you are a blameless nurse.’