‘I thought I heard a noise from below,’ Werner said. He turned the handle but the door had a flimsy lock. He stepped back and raised his right foot.

Macke said: ‘No—’

‘Yes – I hear them!’ Werner said, and he kicked the door open.

The crash resounded throughout the empty factory.

Werner burst through the door and disappeared. A light came on, showing a stone staircase. ‘Don’t move!’ Werner yelled. ‘You are under arrest!’

Macke went down the stairs after him.

He reached the basement. Werner stood at the foot of the stairs, looking baffled.

The room was empty.

Suspended from the ceiling were rails on which coats had probably been hung. An enormous roll of brown paper stood on end in one corner, probably intended for wrapping. But there was no radio and no spy tapping messages to Moscow.

‘You fucking idiot,’ Macke said to Werner.

He turned and ran back up the stairs. Werner ran after him. They traversed the hallway and went up to the next floor.

There were rows of workbenches under a glass roof. At one time the place must have been full of women working at sewing machines. Now there was nobody.

A glass door led to a fire escape, but the door was locked. Macke looked out and saw nobody.

He put his gun away. Breathing hard, he leaned on a workbench.

On the floor he noticed a couple of cigarette ends, one with lipstick on. They did not look very old. ‘They were here,’ he said to Werner, pointing at the floor. ‘Two of them. Your shout warned them, and they escaped.’

‘I was a fool,’ Werner said. ‘I’m sorry, but I’m not used to this kind of thing.’

Macke went to the corner window. Along the street he saw a young man and woman walking briskly away. The man was carrying a tan leather suitcase. As he watched, they disappeared into the railway station. ‘Shit,’ he said.

‘I don’t think they were spies,’ Werner said. He pointed to something on the floor, and Macke saw a crumpled condom. ‘Used, but empty,’ Werner said. ‘I think we caught them in the act.’

‘I hope you’re right,’ said Macke.

(vi)

The day Joachim Koch promised to bring the battle plan, Carla did not go to work.

She probably could have done her usual morning shift and been home in time – but ‘probably’ was not enough. There was always a risk that there might be a major fire or a road accident obliging her to work after the end of her shift to deal with an inrush of injured people. So she stayed at home all day.

In the end Maud had not had to ask Joachim to bring the plan. He had said he needed to cancel his lesson; then, unable to resist the temptation to boast, he had explained that he had to carry a copy of the plan across town. ‘Come for your lesson on the way,’ Maud had said; and he had agreed.