What are the most important things that happened in "The Red-Headed League"?
The first most important event that happen in the story are that John Clay discovered that Mr. Wilson’s shop was perfectly placed for them to dig a tunnel to the bank. Then Clay got himself a job under an assumed name, so that he could persuade Wilson. He placed an ad about the “Red-headed League” and showed Wilson, encouraging him to apply because his hair was so red. Wilson did, and got the job—which turned out to be copying the encyclopedia.
The case piques Holmes’s interest, and he and John go to check out the store. It does not take Holmes long to realize the bank is right there, and he invites the cops to arrest Clay.
The police agree with Holmes that Clay is an unusually brilliant criminal.
John Clay, the murderer, thief, smasher, and forger. He's a young man, Mr. Merryweather, but he is at the head of his profession, and I would rather have my bracelets on him than on any criminal in London.
Of course, they are successful. The mystery of the “Red-headed League” is solved, a robbery is averted, and a master criminal is caught. Just another day on the job for the illustrious Sherlock Holmes!