The Hound of the Baskervilles

"Sir Charles died of a heart attack," said Dr Mortimer. "He was running away from somethin when he died." "What was he running away from?" asked Holmes. "I looked at the ground where Sir Charles had walked," said Dr Mortimer. "There were footprints on the ground. They were not the footprints of a man. They were the footprints of a gigantic hound!"