During our walk Stapleton spoke of the moor and showed me the dreadful Grimpen Mire covered with bright green spots. They looked pleasant, but were treacherous and dangerous.
"It's a terrible place, the great Grimpen Mire. A false step there means death to man or beast."
As the path approached the mire we saw something brown rolling and tossing in the green grass. Then a long neck of a pony rose desperately and a dreadful cry came over the moor. In a moment the animal disappeared.
"It's an awful place," said Stapleton. "Yet I can penetrate into the very heart of it and return alive. I know two safe paths."
"But why do you go into such a dreadful place?" I asked in surprise.
"Because there are rare plants and butterflies beyond those hills," answered the naturalist. "But to reach them I must cross the mire."
Suddenly a long, sad moan swept over the whole moor. It filled the air, yet it was impossible to say where it came from.
"What is it?" I whispered.
"The peasants say it's the hound of the Baskervilles. I've heard it once or twice before, but never so loud," answered Stapleton in a low voice.
"You are an educated man. You cannot believe such nonsense," I exclaimed. "What is the real cause of the sound?"
"Well, there are so many strange things on the moor. Perhaps it was some bird. Oh, excuse me for a moment, Dr Watson."
The naturalist had seen a small butterfly and ran quickly after it, jumping from tuft to tuft straight into the mire. I stood watching him with fear when suddenly I heard a step and, turning round, I saw a woman upon the path. She had come from the direction of Merripit House and I didn't doubt that this was Miss Stapleton, the naturalist's sister.
She was very beautiful. There was a great contrast between the brother and the sister, for Stapleton was rather small, with light hair and grey eyes, while she was dark, elegant and tall. She came up to me and said quickly:
"Go back! Go back to London at once!"
I could only look at her in stupid surprise.
"I cannot explain. But for God's sake do what I ask you. Go back and never set foot upon the moor again."
"But I have just come."
"Go away from this place. Start tonight. Hush, my brother is coming. Not a word of what I have said."
Stapleton had not caught the butterfly and was coming back red and tired.
"Hello, Beryl," he said. It seemed to me that the naturalist was displeased to see his sister there. His small light eyes glanced suspiciously from her to me.
"You have introduced yourselves, I can see."
"Yes, Jack," she answered. "I was telling Sir Henry about the beauties of the moor in spring."
"I'm not Sir Henry Baskerville. I'm only his friend. My name's Dr Watson."
She flushed. "I thought I was talking to Sir Henry. Excuse me. But come on, and see Merripit House, please".
Merripit House looked poor and sad.
"It's a strange place, but still my sister and I are quite happy here," said Stapleton. "I had a school before I came to this part of the country," he continued.
"It was in the North. A serious epidemic broke out and some of the boys died. It was a great blow to me and I couldn't continue my work at the school.
So I decided to leave it and we came to Devonshire. I love botany and zoology and I find such an interesting field of work here that I'm quite satisfied with the place."
"But aren't you dull here?" I asked turning to Miss Stapleton.
"Oh no, I'm never dull," she said quickly. "We have our books, our studies and interesting neighbours."
"Yes," said Stapleton, "Mortimer is a very good companion, and poor Sir Charles was such a wonderful friend. But come upstairs, Dr Watson, and inspect my collection of insects. Lunch will soon be ready."
I was in a hurry to return to Baskerville House. The sadness of the moor, the death of the unfortunate pony, the strange sound connected with the Baskervilles, all worried me. Then there was Miss Stapleton's warning. There must me some serious reason for it. I refused the invitation to lunch and, with my mind full of dark fears, made my way back to Baskerville Hall.