Question

Which event in the story is a key detail in Holmes’s solution of the case?
a. the observation that Mr. Wilson belonged to the Freemasons
b. the walk around Saxe-Coburg Square
c. the invitation to the police agent from Scotland Yard
d. the violin concert at St. James’ Hall

Answer 1

(B) The walk around Saxe-Coburg Square

is the key event in story which leads to Holmes' solution of the case.