The man he brought in was rag and bone inside striped pyjamas. His eyes, which seemed too big for his head, were disconcertingly bright.

'This is Colonel Mike Bradley,' McArthur's friend, Captain Shaw, said to the apparition who stood meekly by the desk. 'He wants to talk to you about Kahla. Here, take a seat.' When the corpse-like individual had sat down, Shaw lit a cigarette and said, 'Colonel Bradley, this is Alex Overbeck. He's been in Buchenwald for two years and somehow survived it. He already knows who you are. Fire away, Colonel.' Then he gave the cigarette to Overbeck and kicked a chair toward Bradley. 'Sit down, Colonel.'

Bradley felt that he had to. He opened his mouth to speak, glanced despairingly at McArthur, received only a forlorn shrug of his shoulders, then looked back at Overbeck, whose eyes, which still seemed too big and too bright, were steady upon him.

'I understand,' Overbeck said, his voice as light as a feather. 'It is difficult to talk when I look like this, but it's not your fault, Colonel. I worked for the American at Kahla. Shall we take it from there? What would you like to know?'

Bradley coughed into his fist and said, 'I didn't even know that Kahla existed. You'd better...'

The gaunt creature smiled. 'Oh, yes, sir, it exists. It is an old walled town, approximately halfway between Erfurt and Nordhausen, and the n.a.z.is constructed another underground factory there, using forced labour from this camp, the closest to it.'

'We don't have a d.a.m.ned thing on it,' Bradley said, gradually getting used to Overbeck's appearance and feeling less ashamed.

When Overbeck inhaled on his cigarette, his cheekbones looked devoid of flesh.

'I had the impression,' he said, 'that even those at Nordhausen didn't know about it. The complex at Kahla was constructed in great haste, at a great cost in human life, and guarded by the SS Death's Head elite. The man in charge of it was SS General Hans Kammler. Next in charge was an SS captain, Ernst Stoll. When Himmler visited Nordhausen, he never came near Kahla and it's widely believed that the other scientists, from Peenemnde, didn't even know that it existed. It was a special place, Colonel.'

'Are you suggesting that even Himmler might not have known about it?'

'I cannot confirm that fact, sir, but I certainly suggest it. That belief was widely held among the Buchenwald inmates who worked at the Kahla complex.'

'And the American, Wilson, was there?'

Overbeck, having survived a living death, was still able to smile and to make it sardonic. 'Yes,' he said, 'the American was working there. I was amazed, but there he was. At first I couldn't believe it it just didn't seem credible but though occasionally, sometimes jokingly, he was referred to as "Kruger," those who worked most closely with him addressed him as Wilson. I noted, further, that though his German was grammatically perfect, it retained the trace of an American accent. Also, though he often wore an SS uniform, it was clear to anyone but a fool that he wasn't a military man - and never had been. Besides, he was too old. That was the biggest joke of all. He looked about sixty an extremely healthy, vigorous sixty but there were rumours that he was much older than that, maybe even by fifteen years. Whether or not there was any truth in those rumours, he was certainly no German soldier, let alone a member of Himmler's SS Death's Head.'

'What did you do in Kahla?' Bradley asked.

Overbeck just shrugged. 'What we all did. I worked.'

'Doing what?'

'Anything they ordered me to do.'

'Let me rephrase the question: What work was the American involved in? What was he constructing?'

'A secret weapon,' Overbeck said, as if it was self-evident. 'Not much different from the work going on at Nordhausen. Rockets, submarines, jet planes... All sorts of highly advanced weapons.'

'And Wilson's? Specifically?'

'A disc-shaped aircraft. Jet-propelled, I think. We all made jokes about eating off the saucer we were so poorly fed, you know. Anyway, that's what he was working on, this saucer-shaped, jetpropelled aircraft that ascended straight up in the air. I hated him to me, he was just a n.a.z.i but his machine was breathtaking.'

'You saw a test flight?'

'I helped wheel it out of the hangar.'

'And it made a vertical ascent?'

'Yes. Then it hovered in the air not moving, just hovering then shot off horizontally so fast, I hardly knew where it went.'

'How fast?'

'Too fast to calculate. And since I can't judge even an aircraft's speed, I wouldn't hazard a guess.'

Bradley smiled. 'What did you do before the war, Mr Overbeck?'

'I was a priest,' Overbeck replied.

Bradley didn't know where to look. The man's strength made him feel weak. He coughed into his fist again, felt foolish, then cleared his throat. 'No wonder you can't judge the speed of aircraft.'

Overbeck blew a cloud of smoke and smiled again, his cheeks prominent. 'Anything else?' he asked.

'Yes. Is Wilson's flying saucer still at Kahla?'

'No,' Overbeck said. 'It was blown up a few days later. I think they destroyed it to keep you or the Soviets from getting your hands on it. Which is why, when they evacuated the site, they executed everyone who'd worked there and took everything with them. I'm a lucky man, Colonel.'

'Sounds like it. How did you escape?'