Every minute that white woolly plain which covered one halfof the moor was drifting closer and closer to the house. Alreadythe first thin wisps of it were curling across the golden square ofthe lighted window. The farther wall of the orchard was alreadyinvisible， and the trees were standing out of a swirl of whitevapour. As we watched it the fog-wreaths came crawling roundboth corners of the house and rolled slowly into one dense bank，on which the upper floor and the roof floated like a strange shipupon a shadowy sea. Holmes struck his hand passionately uponthe rock in front of us and stamped his feet in his impatience.
“If he isn’t out in a quarter of an hour the path will be covered.
In half an hour we won’t be able to see our hands in front of us.”
“Shall we move farther back upon higher ground？”
“Yes， I think it would be as well.”
So as the fog-bank flowed onward we fell back before it untilwe were half a mile from the house， and still that dense whitesea， with the moon silvering its upper edge， swept slowly andinexorably on.
“We are going too far，” said Holmes. “We dare not take thechance of his being overtaken before he can reach us. At all costswe must hold our ground where we are.” He dropped on his kneesand clapped his ear to the ground. “Thank God， I think that Ihear him coming.”
A sound of quick steps broke the silence of the moor. Crouchingamong the stones we stared intently at the silver-tipped bank infront of us. The steps grew louder， and through the fog， as througha curtain， there stepped the man whom we were awaiting. Helooked round him in surprise as he emerged into the clear， starlitnight. Then he came swiftly along the path， passed close to where welay， and went on up the long slope behind us. As he walked he glancedcontinually over either shoulder， like a man who is ill at ease.
“Hist！” cried Holmes， and I heard the sharp click of a cockingpistol. “Look out！ It’s coming！”
There was a thin， crisp， continuous patter from somewhere inthe heart of that crawling bank. The cloud was within fifty yardsof where we lay， and we glared at it， all three， uncertain whathorror was about to break from the heart of it. I was at Holmes’selbow， and I glanced for an instant at his face. It was pale andexultant， his eyes shining brightly in the moonlight. But suddenlythey started forward in a rigid， fixed stare， and his lips parted inamazement. At the same instant Lestrade gave a yell of terror andthrew himself face downward upon the ground. I sprang to myfeet， my inert hand grasping my pistol， my mind paralyzed by thedreadful shape which had sprung out upon us from the shadowsof the fog. A hound it was， an enormous coal-black hound， but notsuch a hound as mortal eyes have ever seen. Fire burst from itsopen mouth， its eyes glowed with a smouldering glare， its muzzleand hackles and dewlap were outlined in flickering flame. Neverin the delirious dream of a disordered brain could anything moresavage， more appalling， more hellish be conceived than that darkform and savage face which broke upon us out of the wall of fog.
With long bounds the huge black creature was leaping downthe track， following hard upon the footsteps of our friend. Soparalyzed were we by the apparition that we allowed him to passbefore we had recovered our nerve. Then Holmes and I both firedtogether， and the creature gave a hideous howl， which showed thatone at least had hit him. He did not pause， however， but boundedonward. Far away on the path we saw Sir Henry looking back， hisface white in the moonlight， his hands raised in horror， glaringhelplessly at the frightful thing which was hunting him down.
But that cry of pain from the hound had blown all our fearsto the winds. If he was vulnerable he was mortal， and if we couldwound him we could kill him. Never have I seen a man runas Holmes ran that night. I am reckoned fleet of foot， but heoutpaced me as much as I outpaced the little professional. Infront of us as we flew up the track we heard scream after screamfrom Sir Henry and the deep roar of the hound. I was in time tosee the beast spring upon its victim， hurl him to the ground， andworry at his throat. But the next instant Holmes had emptied fivebarrels of his revolver into the creature’s flank. With a last howlof agony and a vicious snap in the air， it rolled upon its back， fourfeet pawing furiously， and then fell limp upon its side. I stooped，panting， and pressed my pistol to the dreadful， shimmering head，but it was useless to press the trigger. The giant hound was dead.
Sir Henry lay insensible where he had fallen. We tore away hiscollar， and Holmes breathed a prayer of gratitude when we sawthat there was no sign of a wound and that the rescue had been intime. Already our friend’s eyelids shivered and he made a feebleeffort to move. Lestrade thrust his brandy-flask between thebaronet’s teeth， and two frightened eyes were looking up at us.
“My God！” he whispered. “What was it？ What， in heaven’sname， was it？”
“It’s dead， whatever it is，” said Holmes. “We’ve laid the familyghost once and forever.”
In mere size and strength it was a terrible creature which waslying stretched before us. It was not a pure bloodhound and itwas not a pure mastiff； but it appeared to be a combination of thetwo—gaunt， savage， and as large as a small lioness. Even now， inthe stillness of death， the huge jaws seemed to be dripping with abluish flame and the small， deep-set， cruel eyes were ringed withfire. I placed my hand upon the glowing muzzle， and as I heldthem up my own fingers smouldered and gleamed in the darkness.
“Phosphorus，” I said.
“A cunning preparation of it，” said Holmes， sniffing at the deadanimal. “There is no smell which might have interfered with hispower of scent. We owe you a deep apology， Sir Henry， for havingexposed you to this fright. I was prepared for a hound， but not forsuch a creature as this. And the fog gave us little time to receivehim.”
“You have saved my life.”
“Having first endangered it. Are you strong enough to stand？”