The sign of the four

Several years have passed since "a study in scarlet". John Watson wrote the story of their adventure, thinking that Sherlock would be pleased, but the genius criticizes : there is useless romance, not only facts.

But Watson is mainly worried and upset about his companion drug habit : cocaine or morphine are supposed to stimulate Sherlock's bored mind, but how can he damage his extraordinary capacities ? 
Fortunately, a new case arrives with a charming visitor : Mary Morstan

Ten years ago, Captain Morstan disappeared. He had served in India, leaving his daughter in England. He came back to London, and should have met Mary there, but he never did. His affairs were in his bedroom at the hotel. His only acquaintance, Major Sholto, had no idea of what could have happened to him. 

Four years later, Mary received a very valuable pearl from an anonymous sender, and then each year another one at the same date. But recently, she received a note instead, asking for a meeting. She could come with two friends, and that's why she came to Sherlock, in the hope of solving the mystery of her father's disappearing.

But soon the adventure turns into a treasure hunt.

It's  easy to understand why this story was a success. Even now, the recipe is good : numerous characters, including a dog gifted with an extraordinary nose, street children ("the Baker Street irregulars"), a romance, a treasure, friendship, loyalty, treachery, revenge, an Indian exotic adventure... And a villain who had good reason to become such a bad guy.
Only the "islander" seems a bit strange by-now.

We discover several new aspects of Holmes's character : 

• He alternates excitement with depression; 
• He wrote several monographs related to crime : about tobacco ashes, footprints...
• He's got a "fan" in France, François le Villard, a (good) detective.
• He plays violin; 
• and he likes to give fine dinners ! 

"Watson, you have never yet recognized my merits as a housekeeper"

We also have another view of what he thinks about love, and even about women...

New characters : Mrs Hudson, Wiggins, Mary Morstan
Characters of this novel : Athelney Jones (detective), Tadheus and Bartholomew Sholto, Jonathan Small (villain) and his "islander" (a very little man from Andaman Islands) & Toby the dog