The Sign of Four is Sir Arthur Conan Doyles second book starring legendary detective Sherlock Holmes. The story is complex, involving a secret between four ex-cons from India and a hidden treasure. More complex than the first Holmes novel, The Sign of Four also introduces the detectives drug habit and leaves breadcrumbs for the reader that lead toward the final resolution.
Excerpt from the book:
Sherlock Holmes took his bottle from the corner of the mantelpiece, and his hypodermic syringe from its neat morocco case. With his long, white, nervous fingers he adjusted the delicate needle and rolled back his left shirtcuff. For some little time his eyes rested thoughtfully upon the sinewy forearm and wrist, all dotted and scarred with innumerable puncturemarks. Finally, he thrust the sharp point home, pressed down the tiny piston, and sank back into the velvet-lined armchair with a long sigh of satisfaction.
Three times a day for many months I had witnessed this performance, but custom had not reconciled my mind to it. On the contrary, from day to day I had become more irritable at the sight, and my conscience swelled nightly within me at the thought that I had lacked the courage to protest. Again and again I had registered a vow that I should deliver my soul upon the subject; but there was that in the cool, nonchalant air of my companion which made him the last man with whom one would care to take anything approaching to a liberty. His great powers, his masterly manner, and the experience which I had had of his many extraordinary qualities, all made me diffident and backward in crossing him.
Yet upon that afternoon, whether it was the Beaune which I had taken with my lunch or the additional exasperation produced by the extreme deliberation of his manner, I suddenly felt that I could hold out no longer.”