I was about half-way on my return journey when I heard a car racing along the road behind me, and as it came nearer I detected the fact that it was slowing down. Ere I could turn:  
"Hi! Mr. Addison!" hailed a voice.
 
I stopped, turned round, and there was Gatton leaning out of the car and staring towards me through the deepening dusk.
 
"Why, Gatton!" I said, walking up to him—"I waited more than ten minutes for you, and then gave it up."
 
"Waited for me?"
 
"Yes, by the police-box."
 
He stared in evident wonder at me and then at the police chauffeur who drove the car.
 
"Whatever prompted you to do that?" he said. "Coates must have given you the wrong message. I said I would come to the house for you, not meet you in the street."
 
Still I remained dense to the truth, and:
 
"I know you did," I replied. "I refer to the second message."
 
"I sent no second message."
 
"What!"
 
"Get in," cried Gatton shortly; "this wants explaining."
 
I stepped into the car, and as it moved onward again I explained to the Inspector what had taken place. As I talked I saw his expression grow darker and darker, until finally:
 
"There's something wrong!" he muttered.
 
"Then you did not inspire the message?"
 
"I know nothing whatever about it. At the time you received it I was on my way from Crossleys. I have been traveling for the last hour and a half."
 
I stared at him very blankly. The object of such a communication was difficult to imagine, and I knew of nothing incriminating in my possession, which might have tempted the assassin to lure me from the house whilst he obtained possession of it.
 
In ever-growing excitement I watched the houses slipping behind us as we swept along. Then we came to the tree-lined expanse of road immediately leading to the cottage. As the car stopped, I leaped out quickly, Gatton close upon my heels, and ran up the path to the door.
 
From certain indications with which I was familiar, I observed that Coates was out, whereby I concluded that he had set off to meet the mythical "man with a box." Not without apprehension I inserted the key in the lock and opened the door.
 
As I did so, I beheld a most singular spectacle.
 
The careful Coates had closed all the windows as usual before quitting the house, so that there was comparatively little draught along the corridor. But as the door swung open I perceived a sort of gray fog-like vapor floating over the carpet about a foot in depth and moving in slightly sinuous spirals upward towards the opened door!
 
At this phenomenon I stared in speechless astonishment; for whilst it resembled steam or the early morning mist which one sometimes sees upon the grass in hot weather, I was wholly at a loss to account for its presence inside my cottage!
 
"Good heavens!" cried Gatton, and grasped me by the arm with so strong a grip that I almost cried out. "Look! Look!"
 
"What the devil is it?" I muttered; and turning, I stared into his face. "What can it be?"
 
"Stand back," he said strangely, and pulled me out into the porch. "Do you notice a peculiar smell?"
 
"I do—a most foul and abominable smell."
 
Gatton nodded grimly.
 
"God knows what has happened here since you left," he said; "but of one thing I am sure—you must certainly bear a charmed life, Mr. Addison. There has been a third attempt at your removal!"
 
This choking smell which now rose to my nostrils had in it something vaguely familiar, yet something which at that place and that time I found myself unable to identify; but:
 
"We shall have to open the windows!" rapped Gatton.
 
Suiting the action to the word, he took out his handkerchief, and holding it to his nostrils went running along the corridor, his feet oddly enveloped in that mysterious mist. A moment later I heard the bang of a swiftly raised window, then another, and:
 
"Stand clear of the door!" called a muffled voice.
 
A moment later Gatton came racing back again, coughing and choking because of the fumes which arose from that supernatural fog carpeting the passages.
 
The chauffeur now appeared upon the path leading from the gate to the porch, but:
 
"Stay by the car!" ordered Gatton. "Don't move without instructions."
 
I scarcely noted his words. For I was watching the gray fog. In the dusk I could see it streaming out, that deathly mist, and creeping away across grass and flower-beds, right and left of the door.
 
"Give it a chance to clear," said Gatton; "I fancy one good whiff would finish any man!"
 
Even as he spoke the words the nature of this vapor suddenly occurred to me, and:
 
"The Abbey Inn!" I whispered. "The Abbey Inn!"
 
"Ah!" said he—"you've solved the mystery, have you? But can you explain how this stuff comes to be floating about the floor of your house?"
 
"I cannot," I confessed. "But at all costs we must go in. We must learn the worst!"
 
"Yes, we'll risk it now," said the Inspector.
 
Close together we entered and made our way towards the study. As we passed the door-way of the ante-room in which the telephone was placed. I glanced, aside, and thereupon:
 
"My God, Gatton!" I groaned. "Look!"
 
He pulled up and the two of us stood, horror-stricken, rooted to the spot, looking into the little room.
 
I have said that Coates invariably closed the windows before leaving the house, but here the window was open. Prone upon the floor was stretched the figure of a man!
 
He wore a light overcoat, and his hat lay under the telephone table—where it had evidently rolled at the moment of his fall. The poisonous smell was more apparent here than elsewhere; and looking down at the prone figure, the face of which was indiscernible because of the man's position:
 
"Why, Gatton!" I said in an awed whisper—"look!... he was speaking to some one!"
 
"I'm looking!" replied Gatton grimly.
 
Grasped rigidly in his left hand the fallen man held the telephone!
 
"We want gas-masks for this job," said the Inspector.
 
His words were true enough. I had already recognized the odor of the foul stuff. It was identical with that which, as we had come down from the upper floor of the Abbey Inn, had proceeded from the room wherein the mysterious shell had exploded. In a word my cottage was filled with some kind of poison-gas!
 
"We must risk it, anyway," said Gatton, "and find out who it is."
 
I nodded, sick with foreboding. Stooping swiftly, he succeeded in turning over the prone figure, whereupon I quite failed to restrain a hoarse cry of horror....
 
It was Eric Coverly!
 
The fume-laden room seemed to swim around me as I looked down at the dreadfully contorted features over which was creeping that greenish tint which had characterized the face of Sir Marcus as I had seen it on the morning of the body's recovery from the hold of the Oritoga.
 
"Drag him out," said Gatton huskily; "he may be alive."
 
But even as we bent to the attempt, both my companion and I were seized with violent nausea; for the wisps of gray mist which still floated in the air were nevertheless sufficiently deadly. However, we succeeded at last in dragging Eric Coverly into the passage. Here it became necessary to detach the telephone from the death-grip in which he held it.
 
I turned my head aside whilst Gatton accomplished this task; then together we bore Coverly out into the porch. At this point we were both overcome again by the fumes. Gatton was the first to recover sufficiently to stoop and examine the victim of this fiendish outrage. I clutched dizzily at an upright of the porch, and:
 
"Don't tell me he's dead," I whispered.
 
But Gatton stood up and nodded sternly.
 
"He was the last!" he said strangely. "They have triumphed after all."
 
The man who had driven the car and who now stood in a state of evident stupefaction looking over the gate, where he had been warned to remain by the Inspector, came forward on seeing Gatton beckoning to him.
 
"Notify the local officer in charge and bring a doctor," said Gatton. He turned to me. "Which is the nearest?"
 
Rapidly I gave the man the necessary instructions and he went running out to the car and soon was speeding away towards the house of a local physician.
 
I find it difficult to recapture the peculiar horror of the next few minutes, during which, half-fearful of entering the cottage, Gatton and I stood in the little sheltered garden adjoining the porch looking down at the body of this man who had met his end under my roof, in circumstances at once dreadful and incomprehensible.
 
Tragically, Eric Coverly was vindicated; by his death he was proved innocent. And by the manner of his death we realized that he had fallen a victim to the same malign agency as his cousin.
 
I have explained that my cottage stood in a strangely secluded spot, although so near to the sleepless life of London; and I remember that throughout the period between the departure of the man with the car and his return with the doctor and two police officers whom he had brought from the local depot, only one pedestrian passed my door and he on the opposite side of the road.
 
How little that chance traveler suspected what a scene was concealed from his eyes by the tall hedges which divided the garden from the highroad! It was as the footsteps of this wayfarer became faint in the distance, that suddenly:
 
"Come along!" said Gatton. "We might chance it now. I want to get to the bottom of this telephone trick."
 
We returned to the door of the ante-room, and side by side stood looking down at the telephone which had only been extracted from the grip of the dead man with so much difficulty. The Inspector stooped and took it up from the floor. The deadly gray mist was all but dissipated now, and together we stood staring stupidly at the telephone which Gatton held in his hand.
 
To all outward seeming ............