The Sign of Four

Miss Morstan was the recipient of six rare pearls.... the reason unknown. She has also received a mysterious letter, which she shares with Holmes.

“Thank you,” said Holmes. “The envelope too, please. Postmark, London, S.W. Date, July 7. Hum! Man’s thumb-mark on corner,—probably postman. Best quality paper. Envelopes at sixpence a packet. Particular man in his stationery. No address. ‘Be at the third pillar from the left outside the Lyceum Theatreto-night at seven o’clock. If you are distrustful, bring two friends. You are a wronged woman, and shall have justice. Do not bring police. If you do, all will be in vain. Your unknown friend.’ Well, really, this is a very pretty little mystery. What do you intend to do, Miss Morstan?”