Why does Dr Mortimer need help of Sherlock Holmes?

Answer 1

Because, Sherlock is like the expert at solving crimes.

Dr. Mortimer was one of the principle players in "The Hound of the Baskervilles", whose walking stick was found and shown to Holmes, who was able to deduce much about the man before seeing him. Mortimer needed help with addressing "The Baskerville Curse". :}

Answer 2

". . . . There is only one point on which I must insist. You must not interfere, come what may. You understand?"

___"I am to be neutral?"

___"To do nothing whatever. There will probably be some small unpleasantness. Do not join in it. It will end in my being conveyed into the house. Four or five minutes afterwards the sitting-room window will open. You are to station yourself close to that open window."

___"Yes."

___"You are to watch me, for I will be visible to you."

___"Yes."

___"And when I raise my hand - so - you will throw into the room what I give you to throw, and will, at the same time, raise the cry of fire. You quite follow me?"

___"Entirely."

___"It is nothing very formidable," he said, taking a long cigar-shaped roll from his pocket. "It is an ordinary plumber's smoke rocket, fitted with a cap at either end to make it self-lighting. Your task is confined to that. When you raise your cry of fire, it will be taken up by quite a number of people. You may then walk to the end of the street, and I will rejoin you in ten minutes. I hope that I have made myself clear?"

___"I am to remain neutral, to get near the window, to watch you, and, at the signal, to throw in this object, then to raise the cry of fire, and to await you at the corner of the street."

___"Precisely."

To be clear, a plumber's smoke rocket is basically what is now known as a smoke bomb.

Answer 3

Investigate the death of Sir Charles Baskerville to prevent the death of Sir Henry Baskerville.

Answer 4

He wants Sherlock Holmes to help catch the hound that is causing deaths on the moor.