That evening Holmes and I drove across the moor until we could see the lights of the Stapletons" house in front of us.Then we got out and began to walk very quietly along the path towards the house.When we were very close,Holmes told me to stop.He took his revolver from his pocket,and I did the same. "We shall hide behind these rocks," he whispered." Watson,you know the house,so I want you to go forward and look through the windows.I want to know where the Staple- tons and Sir Henry are,and what they are doing.Take great care,because they must not know that somebody is watching them." Very carefully and quietly I moved towards the house.I looked first into the dining-room window.Statleton and Sir Henry were sitting and smoking their cigars,but there was no sign of Miss Stapleton.I moved round to the other windows,but I could not see her in any of the rooms. I went back to the dining-room window,and as I looked in again,Stapleton left the room and came out of the house.He went to a hut beside the house,and unlocked the door.I heard a strange sound coming from the hut,but I could not think what was making the noise.Then Stapleton locked the door,and went back into the house and into the dining-room. I went back to Holmes and told him what I had seen.He wanted to know where Miss Stapleton was,and I had to tell him twice that there was no sign of her in the house. The moon was shining on the Great Grimpen Marsh,and a fog was rising from it Holmes watched the fog and began to look worried The fog was creeping up from the marsh towards the house.We were hidden near the path,which was on the far side of the house from the marsh. "The fog is moving towards us,Watson,and that is very serious,"said Holmes."It is the one thing that could make my plans go wrong." As we watched,the fog,which had crept as far as the house,began to flow round it.Angrily Holmes hit the rock in front of us with his open hand. "If Sir Henry doesn"t come out in the next quarter of an hour,the path will be covered by the fog.In half an hour we shall not be able to see our hands in front of our faces.We must move back to higher ground above the fog." We moved away from the house and out of the fog,which was creeping slowly along the ground and hiding the path from our view. "We must not go too far,"said Holmes."If we do,Sir Henry may be caught before he reaches us." Holmes went down on one knee,and put his ear to the ground."Thank heaven,I think I hear him coming." Then we heard quick footsteps on the path.After a few moments,Sir Henry appeared out of the fog and walked on in the clear moonlight.He came quickly along the path,passed close to where we were hidden,and began to walk up the hill behind us.As he walked,he looked over his shoulder again and again,like a man who is worried that something is following him. "Listen!"said Holmes sharply."Look out!It"s coming!" I heard him make his revolver ready to fire,and I did the same. There was a sound of quick,light footsteps from inside the curtain of fog.The thick cloud had crept to within fifty metres of where we were hidden.We tried to see into it,and wondered what horrible thing would appear.I looked at Holmes.His eyes were fixed on the place where the path disappeared into the fog.He was pale,but his eyes were bright.He looked like a man who was going to win the most important game of his life.Then suddenly his eyes nearly jumped out of his head,and his mouth opened in frightened surprise.I looked away from him to see what his eyes were fixed on.When I saw the awful shape that was coming towards us out of the fog,my blood turned cold.The revolver nearly fell from my hands,and my whole body froze with fear. I saw a hound,an enormous black hound.It was bigger than any dog I had ever seen.But it was something else that filled us with terror.No human eye had ever seen a hound like this one.Fire came from its open mouth.Its eyes were burning.Flames covered its head and body.It was a more horrible sight than anyone could imagine—a hell-hound sent by the devil.It was not a creature of the natural world. The huge,black,burning hound ran quickly and silently after Sir Henry.Far away along the path we saw him turn and look back at the hound.His face was white in the moonlight and his hands were lifted in horror.He watched helplessly as the terrible creature got closer to him.We were so frozen bythe ghostly and unnatural sight that we let the hound go past us,and we could not move.Our friend was near to death,and we were helpless with fear.