Sherlock Holmes - Deductions

 “At least it cannot be your health,” said he, as his keen eyes darted over her: “so ardent a bicyclist must be full of energy.”
“I nearly fell into the error of supposing that you were typewriting. Of course, it is obvious that it is music.”

“In the country, I presume, from your complexion.”

“Well, well, two of you came over. His reverence is our own homemade article. You had known Ralph Smith in South Africa. You had reason to believe he would not live long. You found out that his niece would inherit his fortune. How’s that — eh?”

“The idea was that one of you was to marry her, and the other have a share of the plunder.”