“I’ll try not to. Thank you so much, sir.”

“Um? Not at all, not at all. Quite the reverse. Good morning. Good morning.”

Alleyn closed the door and stood in a sort of trance for some minutes. Then he screwed his face up sideways, as though in doubt, appeared to come to a decision, consulted the telephone directory, and went to call upon Mr. Harold Sage.

Mr. Sage had a chemist’s shop in Knightsbridge. Inspector Alleyn walked to Hyde Park Corner and then took a bus. Mr. Sage, behind his counter, served an elderly lady with dog powders, designed, no doubt, for a dyspeptic pug which sat and groaned after the manner of his kind at her feet.

“These are our own, madam,” said Mr. Sage. “I think you will find they give the little fellow immediate relief.”

“I hope so,” breathed the elderly lady. “And you really think there’s no need to worry?”

The pug uttered a lamentable groan. Mr. Sage made reassuring noises and tenderly watched them out.

“Yes, sir?” he said briskly, turning to Alleyn.

“Mr. Harold Sage?” asked the inspector.

“Yes,” agreed Mr. Sage, a little surprised.

“I’m from Scotland Yard. Inspector Alleyn.”

Mr. Sage opened his eyes very wide, but said nothing. He was naturally a pale young man.

“There are one or two questions I should like to ask you, Mr. Sage,” continued Alleyn. “Perhaps we could go somewhere a little more private? I shan’t keep you more than a minute or two.”

“Mr. Brayght,” said Mr. Sage loudly.

A sleek youth darted out from behind a pharmaceutical display.

“Serve, please,” said Mr. Sage. “Will you just walk this way?” he asked Alleyn and led him down a flight of dark steps into a store-room which smelt of chemicals. He moved some packages off the only two chairs and stacked them up, very methodically, in a dark corner of the room. Then he turned to Alleyn.

“Will you take a chair?” he asked.

“Thank you. I’ve called to check up one or two points that have arisen in my department. I think you may be able to help us.”

“In what connection?”

“Oh, minor details,” said Alleyn vaguely. “Nothing very exciting, I’m afraid. I don’t want to take up too much of your time. It’s in connection with certain medicines at present on the market. I believe you sell a number of remedies made up from your own prescriptions—such as the pug’s powders, for instance?” He smiled genially.

“Oh—quayte,” said Mr. Sage.

“You do? Right. Now with reference to a certain prescription which you have made up for a Miss Ruth O’Callaghan.”

“Pardon?”

“With reference to a certain prescription you made up for a Miss Ruth O’Callaghan.”

“I know the lady you mean. She has been a customer for quite a while.”

“Yes. This was one of your own prescriptions?”