Excerpt from The Hound of the Baskervilles
Sir Arthur Conan Doyle

The Problem I confess at these words a shudder passed through me. There was a thrill in the doctor's voice which showed that he was himself deeply moved by that which he told us. Holmes leaned forward in his excitement and his eyes had the hard, dry glitter which shot from them when he was keenly interested.

"You saw this?"

"As clearly as I see you."

"And you said nothing?"

"What was the use?"

"How was it that no one else saw it?"

"The marks were some twenty yards from the body and no one gave them a thought. I don't suppose I should have done so had I not known this legend."

"There are many sheep-dogs on the moor?"

"No doubt, but this was no sheep-dog."
The marks were located how far from the body?