“Cause!” said Mr. Mycroft. He looked and sounded so like an old raven as he put his head on one side and uttered “caws,” that I couldn’t help laughing.

“Murder’s no laughing matter!” he remonstrated.

“But surely, cher maître, you sometimes are unwilling to allow that death can ever be through natural causes!”

“Cause? There’s sufficient cause here.”

“Post hoc, propter hoc,” I was glad to get off one of my few classic tags. “Because a lady of uncertain years dies considerably after a fall from which her doctor vouched there were no immediate ill effects, you would surely not maintain that it was on account of the fall that the rhythm of her secondary nervous system struck and stopped for good? And even if it was, who’s to blame?”

“Cause.” At this third quothing of the Raven I let my only comment be a rather longer laugh—and waited for my lecture. Mr. Mycroft did not fail me. He went on: “I’ll own I know nothing about causality in the outer world, for I believe no one does really. But I have spent my life, not unprofitably, in tracing human causality. As you’re fond of Dickens, I’ll illustrate from Copperfield’s Mr. Dick. The causes of King Charles’s head coming off may have been due to four inches of iron going through his neck. I feel on safer ground when I say it was due to his failing to get on with his parliament. You say Miss Hess died naturally—that is to say (1) her death, (2) her accident a fortnight before, and (3) the place where that accident took place, all have only a chance connection. Maybe your case would stand were I not watching another line of causality.”

“You mean a motive?”

“Naturally.”

“But motives aren’t proof! Or every natural death would be followed by a number of unnatural ones—to wit, executions of executors and legatees!”

“I don’t know whether I agree with your rather severe view of human nature. What I do know is that when a death proves to be far too happy an accident for someone who survives, then we old sleuths start with a trail which often ends with our holding proofs that not even a jury can fail to see.”

“Still,” I said, “suspicion can’t always be right!”

What had been no more than an after-lunch sparring-match suddenly loomed up as active service with Mr. Mycroft’s, “Well, the police agree with you in thinking that there’s no proof, and with me in suspecting it is murder. That’s why I’m going this afternoon to view the scene of the accident, unaccompanied—unless, of course, you would care to accompany me?”

I may sometimes seem vain but I know my uses. So often I get a ringside seat because, as Mr. Mycroft has often remarked, my appearance disarms suspicion.