Nash inclined his head solemnly and left the room. While he was away there was a rather uncomfortable silence. Alleyn, looking very remote and polite, made no effort to break it. Nash returned after a few minutes with the now familiar carton, on a silver salver. Alleyn took it and thanked him. Nash departed.

“Here it is,” said the inspector cheerfully. “Oh, yes, Nash was quite right; it has been opened and—let me see—one powder has been taken. That doesn’t amount to much.” He put the carton in his pocket and turned to Lady O’Callaghan. “It seems ridiculous, I know, to worry about so small a matter, but it’s part of our job to pick up every thread, however unimportant. This, I suppose, was the last effort Miss O’Callaghan made to interest Sir Derek in any remedy?”

Again she waited for a few seconds.

“Yes,” she murmured at last, “I believe so.”

“She did not mention another remedy to you after he had been taken to the hospital?”

“Really, Inspector Alleyn, I cannot possibly remember. My sister-in-law talks a great deal about patent medicines. She tries to persuade everyone she knows to take them. I believe my uncle, Mr. James Rattisbon, has already explained this to you. He tells me that he made it quite clear that we did not wish this matter to be pursued.”

“I am afraid I cannot help pursuing it.”

“But Mr. Rattisbon definitely instructed you.”

“Please forgive me,” said Alleyn very quietly, “if I seem to be unduly officious.” He paused. She looked at him with a kind of cold huffiness. After a moment he went on. “I wonder if you have ever seen or read a play called Justice, by Galsworthy? It is no doubt very dated, but there is an idea in it that I think explains far better than I can the position of people who become involved, whether voluntarily or involuntarily, with the Law. Galsworthy made one of his characters—a lawyer, I think—say that once you have set in motion the chariot wheels of Justice, you can do nothing at all to arrest or deflect their progress. Lady O’Callaghan, that is the exact truth. You, very properly, decided to place this tragic case in the hands of the police. In doing so you switched on a piece of complicated and automatic machinery which, once started, you cannot switch off. As the police officer in charge of this case I am simply a wheel in the machine. I must complete my revolutions. Please do not think I am impertinent if I say that neither you nor any other lay person, however much involved, has the power to stop the machine of justice or indeed to influence it in any way whatever.” He stopped abruptly. “I am afraid you will think me impertinent—I have no business to talk like this. If you will excuse me—”

He bowed and turned away.