“I think I can, Stackhurst. Come with me now! And you, Inspector, come along! We will see if we cannot deliver this murderer into your hands.”

Leaving the unconscious man in the charge of my housekeeper, we all three went down to the deadly lagoon. On the shingle there was piled a little heap of towels and clothes left by the stricken man. Slowly I walked round the edge of the water, my comrades in Indian file behind me. Most of the pool was quite shallow, but under the cliff where the beach was hollowed out it was four or five feet deep. It was to this part that a swimmer would naturally go, for it formed a beautiful pellucid green pool as clear as crystal. A line of rocks lay above it at the base of the cliff, and along this I led the way, peering eagerly into the depths beneath me. I had reached the deepest and stillest pool when my eyes caught that for which they were searching, and I burst into a shout of triumph.

“Cyanea!” I cried. “Cyanea! Behold the Lion’s Mane!”

The strange object at which I pointed did indeed look like a tangled mass torn from the mane of a lion. It lay upon a rocky shelf some three feet under the water, water a curious waving, vibrating, hairy creature with streaks of silver among its yellow tresses. It pulsated with a slow, heavy dilation and contraction.

“It has done mischief enough. Its day is over!” I cried. “Help me, Stackhurst! Let us end the murderer forever.”

There was a big boulder just above the ledge, and we pushed it until it fell with a tremendous splash into the water. When the ripples had cleared we saw that it had settled upon the ledge below. One flapping edge of yellow membrane showed that our victim was beneath it. A thick oily scum oozed out from below the stone and stained the water round, rising slowly to the surface.

“Well, this gets me!” cried the inspector. “What was it, Mr. Holmes? I’m born and bred in these parts, but I never saw such a thing. It don’t belong to Sussex.”

“Just as well for Sussex,” I remarked. “It may have been the southwest gale that brought it up. Come back to my house, both of you, and I will give you the terrible experience of one who has good reason to remember his own meeting with the same peril of the seas.”

When we reached my study we found that Murdoch was so far recovered that he could sit up. He was dazed in mind, and every now and then was shaken by a paroxysm of pain. In broken words he explained that he had no notion what had occurred to him, save that terrific pangs had suddenly shot through him, and that it had taken all his fortitude to reach the bank.

“Here is a book,” I said, taking up the little volume, “which first brought light into what might have been forever dark. It is Out of Doors, by the famous observer, J. G. Wood. Wood himself very nearly perished from contact with this vile creature, so he wrote with a very full knowledge. Cyanea capillata is the miscreant’s full name, and he can be as dangerous to life as, and far more painful than, the bite of the cobra. Let me briefly give this extract.

"Whom did she ask for?"

"M. Michel Beaumont," replied the servant.

"Queer. And why has she called?"

"All she said was that it was about the Enghien business... So I thought that... "

"What! The Enghien business! Then she knows that I am mixed up in that business... She knows that, by applying here... "

"I could not get anything out of her, but I thought, all the same, that I had better let her in."

"Quite right. Where is she?"

"In the drawing-room. I've put on the lights."

Lupin walked briskly across the hall and opened the door of the drawing-room:

"What are you talking about?" he said, to his man. "There's no one here."

"No one here?" said Achille, running up.

And the room, in fact, was empty.

"Well, on my word, this takes the cake!" cried the servant. "It wasn't twenty minutes ago that I came and had a look, to make sure. She was sitting over there. And there's nothing wrong with my eyesight, you know."

"Look here, look here," said Lupin, irritably. "Where were you while the woman was waiting?"

"In the hail, governor! I never left the hail for a second! I should have seen her go out, blow it!"

"Still, she's not here now... "

"So I see," moaned the man, quite flabbergasted.

"She must have got tired of waiting and gone away. But, dash it all, I should like to know how she got out!"

"How she got out?" said Lupin. "It doesn't take a wizard to tell that."

"What do you mean?"

"She got out through the window. Look, it's still ajar We are on the ground-floor... The street is almost always deserted, in the evenings. There's no doubt about it."

He had looked around him and satisfied himself that nothing had been taken away or moved. The room, for that matter, contained no knicknack of any value, no important paper that might have explained the woman's visit, followed by her sudden disappearance. And yet why that inexplicable flight?

"Has any one telephoned?" he asked.

"No."

"Any letters?"

"Yes, one letter by the last post."

"Where is it?"

"I put it on your mantel-piece, governor, as usual."

Lupin's bedroom was next to the drawing-room, but Lupin had permanently bolted the door between the two. He, therefore, had to go through the hall again.

Lupin switched on the electric light and, the next moment, said:

"I don't see it... "

"Yes... I put it next to the flower-bowl."

"There's nothing here at all."

"You must be looking in the wrong place, governor."

But Achille moved the bowl, lifted the clock, bent down to the grate, in vain: the letter was not there.

"Oh blast it, blast it!" he muttered. "She's done it... she's taken it... And then, when she had the letter, she cleared out... Oh, the slut!... "

Lupin said:

"You're mad! There's no way through between the two rooms."

"Then who did take it, governor?"

They were both of them silent. Lupin strove to control his anger and collect his ideas. He asked:

"Did you look at the envelope?"

"Yes."

"Anything particular about it?"

""Yes, it looked as if it had been written in a hurry, or scribbled, rather."