I hauled on the doorbell, heard a chime that sounded like something from a clock tower, and gazed back across the street. The woman in the pink dressing gown was getting dressed now. I was still watching when the door opened behind me.

“You certainly couldn’t miss the postman,” I said, speaking German. “Not with a bell like that. It lasts as long as a heavenly choir.” I showed him my ID. “I wonder if I might come in and ask you a few questions.”

A strong smell of ether hung in the air, underscoring the obvious inconvenience of my visit. But Helmut Gregor was a German, and a German knew better than to argue with credentials like mine. The Gestapo no longer existed, but the idea and influence of the Gestapo lived on in the minds of all Germans old enough to know the difference between wedding rings and a set of brass knuckles. Especially in Argentina.

“You’d better come in,” he said, standing politely to one side. “Herr…?”

“Hausner,” I said. “Carlos Hausner.”

“A German working for Central State Intelligence. That’s rather unusual, isn’t it?”

“Oh, I don’t know. There was a time when we were quite good at this sort of thing.”

He smiled thinly and closed the door.

We were standing in a high-ceilinged hallway with a marble floor. I had a brief glimpse of what looked like a surgery at the far end of that hallway, before Gregor closed the frosted door in front of it.

He paused, as if half inclined to force me to ask my questions in the hallway, then he seemed to change his mind and led the way into an elegant sitting room. Beneath an ornate gilt mirror was an elegant stone fireplace and, in front of this, a hardwood Chinese tea table and a couple of handsome leather armchairs. He waved me to one of them.

I sat down and glanced around. On a sideboard was a collection of silver mate gourds and, on the table in front of us, a copy of the Free Press, which was the Nazi-leaning German-language daily. On another table was a photograph of a man wearing plus-fours, riding a bicycle. Another photograph showed a man wearing white tie and tails on his wedding day. In neither of these two photographs did the man have a mustache, and this made it easier for me to remember him as the man I’d met on the steps of Dr. Kassner’s Berlin house back in the summer of 1932. The man he’d called Beppo. The man who was now calling himself Helmut Gregor. Apart from the mustache, he didn’t look so very different. He was not quite forty, and his hair was still thick and dark brown, and without a hint of gray. He wasn’t smiling, but his mouth remained slightly open, his lip curled, like a dog getting ready to growl or to bite. His eyes were different from how I remembered them. They were like the cat’s eyes: wary and watchful and full of nine lives’ worth of dark secrets.

“I’m sorry for disturbing your lunch.” I pointed at a glass of milk and a sandwich that lay uneaten on a silver tray on the floor, next to the leg of his chair. At the same time I wondered if the milk and the sandwich might have been meant for his young female visitor.

“That’s all right. What can I do for you?”

I rattled off the usual spiel about the Argentine passport and the good-conduct pass and how everything was nothing more than a formality because I was ex-SS myself and knew the score. Hearing this, he asked me about my war service, and after I’d supplied the edited version that left out my time with the German War Crimes Bureau, he seemed to relax a little, like a fishing line slackening after several minutes in the water.

“I was also in Russia,” he said. “With the medical corps of the Viking Division. And in particular, at the Battle of Rostow.”

“I heard it was tough there,” I offered.

“It was tough everywhere.”

I opened the file I had brought with me. Helmut Gregor’s file. “If I could just check a few basic details.”

“Certainly.”

“You were born on-?”

“March 16, 1911.”

“In?”

“Gunzburg.”

I shook my head. “It’s somewhere on the Danube. That’s as much as I know about it. I’m from Berlin, myself. No. Wait a minute. There was someone I knew who was from Gunzburg. A fellow named Pieck. Walter Pieck. He was in the SS, too. At Dachau concentration camp, I think it was. Perhaps you knew him.”

“Yes. His father was the local police chief. We knew each other slightly, before the war. But I was never at Dachau. I was never at any concentration camp. As I said, I was in the Viking Division of the Waffen-SS.”

“And what did your own father do? In Gunzburg?”

“He sold-still sells-farm machinery. Threshing machines, that kind of thing. All very ordinary. But I believe he’s still the town’s largest employer.”

“I’m sorry,” I said, pen poised. “I’ve missed a question. Name of father and mother, please.”

“Is this really necessary?”

“It’s normal on most passport applications.”

He nodded. “Karl and Walburga Mengele.”

“Walburga. That’s an unusual name.”

“Yes. Isn’t it? Walburga was an English saint who lived and died in Germany. I assume you’ve heard of Walpurgis Night? On the first of May? That’s when her relics were transferred to some church or other.”

“I thought that was some kind of Witches’ Sabbath.”

“I believe it’s also that,” he said.

“And you are Josef. Any brothers or sisters?”

“Two brothers. Alois and Karl Junior.”

“I won’t keep you much longer, Dr. Mengele.” I smiled.

“I prefer Dr. Gregor.”

“Yes, of course. I’m sorry. Now then. Where was it that you qualified?”

“Why is this relevant?”

“You’re still practicing as a doctor, aren’t you? I should say it was highly relevant.”

“Yes. Yes, of course. I’m sorry. It’s just that I’m not used to answering so many questions, truthfully. I’ve spent the last five years being someone else. I’m sure you know what that’s like.”

“I certainly do. Now perhaps you understand why it is that the Argentine government asked me to carry out this task. Because I’m a German and an SS man, just like you. In order that you and our other old comrades could be put at ease about the whole process. You can see that, can’t you?”

“Yes. It makes quite a lot of sense, when you think about it.”

I shrugged. “On the other hand, if you don’t want to have an Argentine passport, we can stop this right now.” I shook my head. “I mean, it certainly won’t make me itch, as the saying goes.”

“Please, do carry on.”

I frowned, as if thinking of something else.

“I insist,” he added.

“No, it’s just that I’ve got a feeling we’ve met before.”

“I don’t think so. I’m sure I would have remembered.”

“In Berlin, wasn’t it? The summer of 1932.”

“In the summer of 1932, I was in Munich.”

“Yes, surely you remember. It was at the home of another doctor. Dr. Richard Kassner. On Donhoff-Platz?”

“I don’t recall knowing a Dr. Kassner.”

I unbuttoned my coat so that I could treat his eyes to a little taste of the gun I was wearing. Just in case he thought to try something surgical on me. Like trepanning a little hole in my head with a pistol. Because by now I had no doubt he was armed. There was something heavier than a packet of cigarettes in one of his coat pockets. I didn’t know exactly what Mengele had done during the war. The only thing I knew was what Eichmann had told me. That Mengele had done something bestial at Auschwitz. And for this reason he was one of the most wanted men in Europe.

“Come now. Surely you remember. What was it he used to call you? Biffo, wasn’t it? No, wait a minute. It was Bippo. Whatever happened to Kassner?”

“I really think you’re mistaking me for someone else. If you don’t mind me saying so, this was eighteen years ago.”

“No, it’s all coming back to me now. You see, Herr Doktor Mengele-Beppo-I was a policeman in 1932. Working for the Homicide Division in Berlin KRIPO. A detective investigating the murder of Anita Schwarz. Do you remember her, perhaps?”