Under the Berlin Pact, Germany was supposed to take Japan’s side in any war with America. Would Hitler keep his promise? If so, then the world would explode.

The few people out at this time of night moved like ghosts through the steady rainfall. There were no street lights and the waning moon was obscured by cloud. Someone had, however, marked some of the pavement edges with luminous paint, the sort used on watch faces. And that helped him find his way.

Vanderberg was exhausted and soaking when he arrived home. As he put the key in the lock, he was still on edge. He was turning the handle when he heard a voice. As he pushed open the door, a little yellow light streamed out from a single low-wattage bulb, just enough for him to see a pitiful figure emerge from the dark. It was the woman who had come to him before, the midwife Romy Dietrich. But it couldn’t be Frau Dietrich, could it? She had been murdered in her block of flats.

‘My God,’ he said. ‘I thought you were dead.’

He pulled her inside the front hall and quickly shut the door after them. She was bent and shaking, one hand in the pocket of a grey, outsized coat that was so stained and worn, it looked as though it had been stripped from a dead soldier. Her fair hair was lank, wet and thin. Her face was drawn, her forehead had an angry bruise and her eyes were flickering and fearful.

‘I am so sorry.’ she said. ‘I followed you from the embassy . . . I did not know what else to do. I have nowhere else to turn.’

‘Hush, let me take you up to my rooms.’

He helped her up the staircase and was relieved that the landlady did not poke her nose around her door to see who he was bringing home; she must be asleep, he thought.

‘Come in, Frau Dietrich,’ Vanderberg said. ‘Sit down. I’ll get you some coffee – perhaps with a little rum.’

‘Thank you.’

‘I’m just relieved to find you alive. I went to your apartment and was told there had been a murder. I feared the worst.’

‘They killed my landlady, Frau Schlegel. They broke her neck in front of my eyes – and then they forced me into a van.’

Slowly and painfully she removed her left hand from her coat pocket. The bandage, a strip of cotton rag, was streaked with dried blood.

He sucked in a breath. ‘What did they do to you?’

‘They wanted to find Klara. They ripped out my fingernails one by one to make me reveal her whereabouts. They would have killed me, but I . . . escaped.’

She couldn’t continue. She was thinking of the wall in the piggery, of the pliers, of the blank-eyed farmwife. She started weeping, her chest heaving.

He knelt at her side. ‘Take your time, Frau Dietrich.’