The Sign Of Four

A young lady named Mary Morstan came to consult Holmes upon a case which she is assure is very unusual. Miss Morstan's father has been disappeared several years previously under suspicious circumstances. He had obtained twelve months leave from his Indian regiment and asked her to meet him at his hotel. Whilst the hotel confirmed that he has been staying there and they informed Miss Morstan that he had gone out and not returned. Enquiries at the time have produced no result. A few years after this disappearance have appeared an advertisement in a paper asking for Miss Morstan to reveal her address. Upon the advice of her employer she has done it and the same day she has received a valuable pearl in the post. Since she has been receiving 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 permitted her to bring two friends but they wouldn't be policemen.