sent for you, and you treated him skilfully and left
him in a fair way to recovery. That's all that we really know about it.
Yes, I know," the officer continued as I made signs of disagreement,
"you think that a crime is possibly going to be committed and that we
ought to prevent it. But you overrate our powers. We can only act on
evidence that a crime has actually been committed or is actually being
attempted. Now we have no such evidence. Look at your statement, and
tell me what you can swear to."

"I think I could swear that Mr. Graves had taken a poisonous dose of
morphine."

"And who gave him that poisonous dose?"

"I very strongly suspect--"

"That's no good, sir," interrupted the officer. "Suspicion isn't
evidence. We should want you to swear an information and give us enough
facts to make out a <i>prima facie</i> case against some definite person. And
you couldn't do it. Your information amounts to this: that a certain
person has taken a poisonous dose of morphine and apparently recovered.
That's all. You can't swear that the names given to you are real names,
and you can't give us any address or even any locality."

"I took some compass bearings in the carriage," I said. "You could
locate the house, I think, without much difficulty."

The officer smiled faintly and fixed an abstracted gaze on the clock.

"<i>You</i> could, sir," he replied. "I have no doubt whatever that <i>you</i>
could. <i>I</i> couldn't. But, in any case, we haven't enough to go upon. If
you learn anything fresh, I hope you will let me know; and I am very
much obliged to you for taking so much trouble in the matter. Good
evening sir. Good evening, Dr. Stillbury."

He shook hands with us both genially, and, accepting perforce this very
polite but unmistakable dismissal, we took our departure.

Outside the station, Stillbury heaved a comfortable sigh. He was
evidently relieved to find that no upheavals were to take place in his
domain.

"I thought that would be their attitude," he said, "and they are quite
right, you know. The function of law is to prevent crime, it is true;
but prophylaxis in the sense in which we understand it is not possible
in legal practice."

I assented without enthusiasm. It was disappointing to find that no
precautionary measures were to be taken. However, I had done all that I
could in the matter. No further responsibility lay upon me, and, as it
was practically certain that I had seen and heard the last