The first main event in the story is when Watson arrives at Sherlock Holmes’s house and he has a visitor by the name of Mr. Wilson. Mr. Holmes asks Watson to stay because he is interested in the unusual, and Mr. Wilson has quite an unusual story to tell.
Mr. Wilson has sought Holmes’s help because he was recently hired by the Red-headed League and paid well to sit 4 hours a day in an office copying an encyclopedia. He is upset when one day the office just closes down.
He held up a piece of white cardboard about the size of a sheet of note-paper. It read in this fashion:
THE RED-HEADED LEAGUE
October 9, 1890. (p. 10)
Holmes and Watson’s reaction is to burst out laughing, but Holmes admits that the case is interesting and agrees to take it.
Holmes thinks for a while and decides to visit Wilson’s shop surreptitiously and meet his assistant. He recognizes him and notes that his trousers are dirty at the knees. His suspicions are confirmed when he taps the sidewalk to see if it is hollow.
Holmes arranges for a policeman named Jones to wait in the bank with him, and they apprehend the criminal.