“Speaking from memory, I think she has had several of my little lines—from tayme to tayme.”

“Yes. Do you remember a drug you supplied three weeks ago?”

“I’m afraid I don’t remember off-hand—”

“This is the one that contained hyoscine,” said Alleyn. In the long silence that followed Alleyn heard the shop-door buzzer go, heard footsteps and voices above his head, heard the sound of the Brompton Road train down beneath them and felt its vibration. He watched Harold Sage. If there was no hyoscine in any of the drugs, the chemist would say so, would protest, would be bewildered. If there was hyoscine, an innocuous amount, he might or might not be flustered. If there was hyoscine, a fatal amount—what would he say?

“Yes,” said Mr. Sage.

“What was the name of this medicine?”

“‘Fulvitavolts.’”

“Ah, yes. Do you know if she used it herself or bought it for anyone else?”

“I reely can’t say. For herself, I think.”

“She did not tell you if she wanted it for her brother?”

“I reely don’t remember, not for certain. I think she said something about her brother.”

“May I see a packet of this medicine?”

Mr. Sage turned to his shelves, ferreted for some time and finally produced an oblong package. Alleyn looked at the spirited picture of a nude gentleman against an electric shock.

“Oh, this is not the one, Mr. Sage,” he said brightly. “I mean the stuff in the round box—so big—that you supplied afterwards. This has hyoscine in it as well, has it? What was the other?”

“It was simply a prescription. I—I made it up for Miss O’Callaghan.”

“From a doctor’s prescription, do you mean?”

“Yes.”

“Who was the doctor?”

“I reely forget. The prescription was returned with the powder.”

“Have you kept a record?”

“No.”

“But surely you have a prescription-book or whatever it is called?”

“I—yes—but—er—an oversight—it should have been entered.”

“How much hyoscine was there in this prescription?”

“May I ask,” said Mr. Sage, “why you think it contained hyoscine at all?”

“You have made that quite clear yourself. How much?”

“I—think—about one two-hundredth—something very small.”

“And in ‘Fulvitavolts’ ?”

“Less. One two-hundred-and-fiftieth.”

“Do you know that Sir Derek O’Callaghan was probably murdered?”

“My Gawd, yes.”

“Yes… With hyoscine.”

“My Gawd, yes.”

“Yes. So you see we want to be sure of our facts.”

“He ’ad no hoverdose of ’yoscine from ’ere,” said Mr. Sage, incontinently casting his aitches all over the place.

“So it seems. But, you see, if he had taken hyoscine in the minutest quantity before the operation we want to trace it as closely as possible. If Miss O’Callaghan gave him ‘Fulvitavolts’ and this other medicine, that would account for some of the hyoscine found at the post-mortem. Hyoscine was also injected at the operation. That would account for more.”