We went up to his apartment. The place was modern. A lot of bleached burr walnut and cream leather and bronzes of naked ladies standing on tiptoe. He opened a cocktail cabinet the size of a sarcophagus and helped himself to a drink. He didn’t offer me one. We both knew that I didn’t deserve to have a drink. He sat down and put his drink on a scallop-edged wooden coaster that was on a scallop-edged coffee table. He crossed his legs and silently invited me to sit down.

“Nice place,” I lied. “Live here alone?”

“Yes. Now what’s this all about, Commissar?”

“There was a girl found dead in Friedrichshain Park several nights ago. She’d been murdered.”

“Yes, I read about it in Tempo. Terrible. But I don’t see-”

“I found one of your protonsil pills near the body.”

“Ah. I see. And you think one of my patients might be the culprit.”

“It’s a possibility I’d like to explore, sir.”

“Of course, it might just be a coincidence. One of my patients walking home from the clinic could have dropped his pills several hours before the body was found.”

“I don’t buy that. The pill hadn’t been there that long. There was a shower of rain that afternoon. The pill we found was in pristine condition. Then there’s the girl herself. She was a juvenile prostitute.”

“Lord, how very shocking.”

“One theory I’m exploring is that the killer may have contracted venereal disease from a prostitute.”

“Thus giving him a motive to kill one. Is that it?”

“It’s a possibility I’d like to explore.”

Kassner sipped his drink and nodded thoughtfully.

“So why that stupid pantomime in the clinic?”

“I wanted to see a list of patients you were treating.”

“Couldn’t you have asked to see it legitimately?”

“Yes. But you wouldn’t have shown it to me.”

“That’s quite right. I wouldn’t. I couldn’t. It would have been unethical.” He smiled. “So what are you? A memory man? Did you hope to remember every name on the list?”

“Something like that.” I shrugged.

“But there were rather more names than you had bargained for. Which is why you’re back here now. And at my home rather than the clinic, because you hoped that this might make it easier for me to forget my doctor-patient duty of confidentiality.”

“Something like that, yes.”

“My first duty, Commissar, is to my patients. Some of whom are very dangerously ill. Suppose for a moment that I did share information regarding their true identities with you. And suppose you chose to interview some of them. All of them. I don’t know. They might very well feel I’d betrayed their confidence. They might never again return to the clinic to complete their treatment. In which case they might very easily go and infect someone else. And so on, and so on.” He shrugged. “You do see what I mean? I regret the murder of anyone. However, I do have to be mindful of the bigger picture.”

“Here’s my bigger picture, Dr. Kassner. The person who killed Anita Schwarz is a psychopath. She was horribly mutilated. The kind of person who kills like that usually does it again. I want to find this maniac before that happens. Are you prepared to have another murder on your conscience?”

“You make a very fair point, Commissar. It’s quite a dilemma, isn’t it? Perhaps the best thing would be to put the matter before the Prussian Medical Ethics Committee and let them decide.”

“How long would that take?”

Kassner looked vague. “A week or two? Perhaps a month.”

“And what do you think they would decide?”

He sighed. “I would never like to second-guess a medical ethics committee. I’m sure it’s the same in the police. There are always proper procedures to be observed. Although they don’t really seem to have been observed here. I wonder what your superiors would make of your conduct toward me?” He shook his head. “But let us suppose that the committee turns down your request. That’s a realistic possibility, I think. What could you do then? I suppose you could try to interview everyone coming in and out of the clinic. Of course, it’s only a small percentage who are in the clinical trial. The vast majority of my patients-and I do mean a vast majority, Commissar-is still using neosalvarsan. And what would happen then? Why, you would frighten people away, of course. And we would have an epidemic of venereal disease in Berlin. As things stand now, we are barely controlling the disease. There are tens of thousands of people in this city suffering from jelly, as you call it. No, Commissar, my own suggestion to you would be to try to find a separate line of inquiry. Yes, sir, I do believe that would be the best thing for all concerned.”

“You make some good points, Doctor,” I said.

“I’m so glad you think so.”

“However, when I was in your office, I couldn’t help noticing that one of the addresses on your list of patients using protonsil is this address. Perhaps you’d care to comment on that.”

“I see. That was very sharp of you, Commissar. I suppose you think that might make me a suspect.”

“It’s a possibility I can’t afford to ignore, sir.”

“No, of course not.” Kassner finished his drink and got up to pour himself another. But I still wasn’t on his list of people he wanted to have a drink with. “Well, then, it’s like this. It’s not uncommon for doctors to infect themselves with a disease they’re trying to cure.” He sat down again, burped discreetly behind his glass, and then toasted me silently.

“Is that what you’re saying, Doctor? That you deliberately infected yourself with a venereal disease to test protonsil on yourself?”

“That’s exactly what I’m saying. Sometimes it’s not enough to test the side effects of a drug on other people. They are less able to describe the full effects of a drug on the human body. As I believe I stated when first we met, it’s rather difficult to keep tabs on patients in these cases. Sometimes the only patient one can really trust is oneself. I’m sorry if you think that makes me a suspect. But I can assure you that I’ve never murdered anyone. As it happens, though, I believe I can supply an alibi for the day and night of that poor girl’s death.”

“I’m delighted to hear it.”

“I was attending a urologists’ conference, in Hannover.”

I nodded and took out my cigarettes. “Do you mind?”

He shook his head and sipped some of his drink. The alcohol hit his stomach and made it start rumbling.

“Here’s what I’d like to suggest, Doctor. Something that might help this inquiry. Something you might like to do voluntarily that wouldn’t offend your sense of ethics.”

“If it’s within my power.”

I lit my cigarette and leaned forward so I was in range of the scallop-edged ashtray.

“Have you ever had any psychiatric training, sir?”

“Some. As a matter of fact, I did my medical training in Vienna and went to several lectures on psychiatry. Once I even considered working in the field of psychotherapy.”

“If you are agreeable, I’d like you to look over all your own patient notes. See if there’s any one of them who perhaps stands out as a possible murderer.”

“And supposing there was? One patient who stood out. What then?”

“Why, then we could discuss the matter. And perhaps discover some mutually acceptable way forward.”

“Very well. I can assure you I’ve no desire to see this man kill again. I have a daughter myself.”

I glanced around the apartment.

“Oh, she lives with her mother, in Bavaria. We’re divorced.”

“I’m sorry.”

“Don’t be.”

“And the man who was here when I called earlier on today?”

“Ah, you must mean Beppo. He’s a friend of my wife’s and came to collect some of her things in his car. He’s a student, in Munich.” Kassner yawned. “I’m sorry, Commissar, but it’s been a very long day. Is there anything else? Only I’d like to take a bath. You can’t imagine how much I look forward to taking a bath after a day in the clinic. Well, perhaps you can imagine.”