Why did Dr Mortimer come to Holmes? Chapter 3

Dr. Mortimer went to Holmes about the circumstances of the death of his friend Sir Charles Baskerville. When Holmes questions why Mortimer come to him, Mortimer explains that Sir Charles's nephew and the next heir, Sir Henry Baskerville, is to arrive in London, and Dr. Mortimer is worried for his safety. He believes that it is important for the moor community to keep a resident in Baskerville Hall, one who can continue Sir Charles's philanthropy, or he would otherwise simply warn Sir Henry away.