“Pangs shot through the chest, causing me to fall as if struck by a bullet. The pulsation would cease, and then the heart would give six or seven leaps as if it would force its way through the chest.

“It nearly killed him, although he had only been exposed to it in the disturbed ocean and not in the narrow calm waters of a bathing-pool. He says that he could hardly recognize himself afterwards, so white, wrinkled and shrivelled was his face. He gulped down brandy, a whole bottleful, and it seems to have saved his life. There is the book, Inspector. I leave it with you, and you cannot doubt that it contains a full explanation of the tragedy of poor McPherson.”

“And incidentally exonerates me,” remarked Ian Murdoch with a wry smile. “I do not blame you, Inspector, nor you, Mr. Holmes, for your suspicions were natural. I feel that on the very eve of my arrest I have only cleared myself by sharing the fate of my poor friend.”

“No, Mr. Murdoch. I was already upon the track, and had I been out as early as I intended I might well have saved you from this terrific experience.”

“But how did you know, Mr. Holmes?”

“I am an omnivorous reader with a strangely retentive memory for trifles. That phrase ‘the Lion’s Mane’ haunted my mind. I knew that I had seen it somewhere in an unexpected context. You have seen that it does describe the creature. I have no doubt that it was floating on the water when McPherson saw it, and that this phrase was the only one by which he could convey to us a warning as to the creature which had been his death.”

“Then I, at least, am cleared,” said Murdoch, rising slowly to his feet. “There are one or two words of explanation which I should give, for I know the direction in which your inquiries have run. It is true that I loved this lady, but from the day when she chose my friend McPherson my one desire was to help her to happiness. I was well content to stand aside and act as their go-between. Often I carried their messages, and it was because I was in their confidence and because she was so dear to me that I hastened to tell her of my friend’s death, lest someone should forestall me in a more sudden and heartless manner. She would not tell you, sir, of our relations lest you should disapprove and I might suffer. But with your leave I must try to get back to The Gables, for my bed will be very welcome.”

Stackhurst held out his hand. “Our nerves have all been at concert-pitch,” said he. “Forgive what is past, Murdoch. We shall understand each other better in the future.” They passed out together with their arms linked in friendly fashion. The inspector remained, staring at me in silence with his ox-like eyes.

“Well, you’ve done it!” he cried at last. “I had read of you, but I never believed it. It’s wonderful!”

I was forced to shake my head. To accept such praise was to lower one’s own standards.

“I was slow at the outset - culpably slow. Had the body been found in the water I could hardly have missed it. It was the towel which misled me. The poor fellow had never thought to dry himself, and so I in turn was led to believe that he had never been in the water. Why, then, should the attack of any water creature suggest itself to me? That was where I went astray. Well, well, Inspector, I often ventured to chaff you gentlemen of the police force, but Cyanea capillata very nearly avenged Scotland Yard.”