This downloadable file type is .ePub (for Sony Reader, Barnes and Nobile Nook, BeBook, Bookeen, Cool-ER, Hanlin eReader, Hanvon, and many other eBook readers.)
Please find .mobi file for all kinds of Amazon eBook reader @ https://www.tradebit.com

Preview;

At the outset of the novel Doctor Watson states that he has been watching Holmes takes cocaine three times a day for many months. Watsons reluctance to oppose Holmes is finally overcome and he confronts his friend about the potential ill effects of this prolonged usage.
Holmes explains that he finds the drug stimulates and clarifies his mind and that without work to challenge his mental faculties he becomes bored with day to day life.

A young lady named Mary Morstan comes to consult Holmes upon a case which she assures him is very unusual. Miss Morstans father disappeared some years previously under suspicious circumstances. He had obtained twelve months leave from his Indian regiment and sent word to her to meet him at his hotel. Whilst the hotel confirmed that he was staying there they informed Miss Morstan that he had gone out and not returned. Enquiries at the time produced no result. Major Sholto was Morstans only known friend in London, the two had been in the same regiment together. Sholto had retired from service at that time and claimed not to have even known that Morstan was in the country.

A few years after this disappearance an advertisement appeared in a paper asking for Miss Morstan to reveal her address. Upon the advice of her employer she did so and that same day she received a valuable pearl in the post. Since then she has received one pearl a year for the last six years.

Miss Morstan has now received a letter which urges her to meet with the sender that night. The anonymous sender permits her to bring two friends as long as they are not police. Later that night on their way to the rendezvous Miss Morstan tells Holmes that Sholto and her father were in charge of the convict guard at the Andaman Islands. She also shows Holmes a strange paper which was found among her fathers things after he disappeared, the document appears to be a map and written upon it are the words the sign of four along with three Indian names and one English name.

Holmes discovers that Major Sholto died about six years previously, within a week of the date of his passing Miss Morstan received her first pearl. This fact suggests that Sholtos heir knows how Captain Morstan died and wishes to make reparation to Miss Morstan.