In a flash I realized all this and sprang to Smith’s assistance.  There was a sound of racing footsteps and the men who had been watching outside came running into the porch.  A third was with them; and the five of us (for Weymouth’s brother had not yet grasped the fact that a man and not a spirit shrieked and howled in our midst) clung to the infuriated madman, yet barely held our own with him.

“The syringe, Petrie!” gasped Smith.  “Quick!  You must manage to make an injection!”

I extricated myself and raced into the cottage for my bag.  A hypodermic syringe ready charged I had brought with me at Smith’s request.  Even in that thrilling moment I could find time to admire the wonderful foresight of my friend, who had divined what would befall—­isolated the strange, pitiful truth from the chaotic circumstances which saw us at Maple Cottage that night.

Let me not enlarge upon the end of the awful struggle.  At one time I despaired (we all despaired) of quieting the poor, demented creature.  But at last it was done; and the gaunt, blood-stained savage whom we had known as Detective-Inspector Weymouth lay passive upon the couch in his own sitting-room.  A great wonder possessed my mind for the genius of the uncanny being who with the scratch of a needle had made a brave and kindly man into this unclean, brutish thing.

Nayland Smith, gaunt and wild-eyed, and trembling yet with his tremendous exertions, turned to the man whom I knew to be the messenger from Scotland Yard.

“Well?” he rapped.

“He is arrested, sir,” the detective reported.  “They have kept him at his chambers as you ordered.”

“Has she slept through it?” said Smith to me.  (I had just returned from a visit to the room above.) I nodded.

“Is he safe for an hour or two?”—­indicating the figure on the couch.  “For eight or ten,” I replied grimly.

“Come, then.  Our night’s labors are not nearly complete.”

CHAPTER XXX

Later was forthcoming evidence to show that poor Weymouth had lived a wild life, in hiding among the thick bushes of the tract of land which lay between the village and the suburb on the neighboring hill.  Literally, he had returned to primitive savagery and some of his food had been that of the lower animals, though he had not scrupled to steal, as we learned when his lair was discovered.

He had hidden himself cunningly; but witnesses appeared who had seen him, in the dusk, and fled from him.  They never learned that the object of their fear was Inspector John Weymouth.  How, having escaped death in the Thames, he had crossed London unobserved, we never knew; but his trick of knocking upon his own door at half-past two each morning (a sort of dawning of sanity mysteriously linked with old custom) will be a familiar class of symptom to all students of alienation.

I revert to the night when Smith solved the mystery of the knocking.