The sound of the piano ceased and, a little later, Carla heard two voices in the hallway, her mother’s and a man’s. She assumed Maud was seeing Herr Koch out, and she was horrified, a moment later, when her mother entered the kitchen, closely followed by a man in an immaculate lieutenant’s uniform.

‘This is my daughter,’ Maud said cheerfully. ‘Carla, this is Lieutenant Koch, a new pupil.’

Koch was an attractive, shy-looking man in his twenties. He had a fair moustache, and reminded Carla of pictures of her father when young.

Carla’s heart raced with fear. The basket containing the stolen medical supplies was on the kitchen chair next to her. Would she accidentally betray herself to Lieutenant Koch, as she had to Frieda?

She could hardly speak. ‘I–I–I am pleased to make your acquaintance,’ she said.

Maud looked at her with curiosity, surprised at her nervousness. All Maud wanted was for Carla to be nice to the new pupil in the hope that he would continue his studies. She saw no harm in bringing an army officer into the kitchen. She had no idea that Carla had stolen medicines in her shopping basket.

Koch made a formal bow and said: ‘The pleasure is mine.’

‘And Ada is our maid.’

Ada shot him a hostile look, but he did not see it: maids were beneath his notice. He put his weight on one leg and stood lopsided, trying to seem at ease but giving the opposite impression.

He acted younger than he looked. There was an innocence about him that suggested an over-protected child. All the same he was a danger.

Changing his stance, he rested his hands on the back of the chair on which Carla had put her basket. ‘I see you are a nurse,’ he said to her.

‘Yes.’ Carla tried to think calmly. Did Koch have any idea who the von Ulrichs were? He might be too young to know what a social democrat was. The party had been illegal for nine years. Perhaps the infamy of the von Ulrich family had faded away with the death of Walter. At any rate, Koch seemed to take them for a respectable German family who were poor simply because they had lost the man who had supported them, a situation in which many well-bred women found themselves.

There was no reason he should look in the basket.

Carla made herself speak pleasantly to him. ‘How are you getting on with the piano?’

‘I believe I am making rapid progress!’ He glanced at Maud. ‘So my teacher tells me.’

Maud said: ‘He shows evidence of talent, even at this early stage.’ She always said that, to encourage them to pay for a second lesson; but it seemed to Carla that she was being more charming than usual. She was entitled to flirt, of course; she had been a widow for more than a year. But she could not possibly have romantic feelings for someone half her age.

‘However, I have decided not to tell my friends until I have mastered the instrument,’ Koch added. ‘Then I will astonish them with my skill.’