WHO WAS UNEXPECTED VISITOR WHO CAME AFTER HELEN STONER LEFT ? WHAT DID HE TELL HOLMES AND WATSON?

From the text:

A large face, seared with a thousand wrinkles, burned yellow with the sun, and marked with every evil passion, was turned from one to the other of us, while his deep-set, bile-shot eyes, and his high, thin, fleshless nose, gave him somewhat the
resemblance to a fierce old bird of prey.
“Which of you is Holmes?” asked this apparition.
“My name, sir; but you have the advantage of me,” said my companion quietly.
“I am Dr. Grimesby Roylott, of Stoke Moran.”

“I will go when I have said my say. Don’t you dare to meddle with my affairs. I know that Miss Stoner has been here. I traced her! I am a dangerous man to fall foul of! See here.” He stepped swiftly forward, seized the poker, and bent it into
a curve with his huge brown hands.