The Sign of the Four (1890), also called The Sign of Four, is the second novel featuring Sherlock Holmes written by Sir Arthur Conan Doyle. Doyle wrote four novels and 56 stories starring the fictional detective.

The story is set in 1888. The Sign of the Four has a complex plot involving service in East India Company, India, the Indian Rebellion of 1857, a stolen treasure, and a secret pact among four convicts ("the Four" of the title) and two corrupt prison guards. It presents the detective'...

These essays, upon different phases of the wonderful world- drama which has made our lifetime memorable, would be unworthy of republication were it not that at such a time every smallest thing which may help to clear up a doubt, to elucidate the justice of our cause, or to accentuate the desperate need of national effort, should be thrown into the scale. The longest essay appeared in The Fortnightly Review and the shorter ones for the most part in The Daily Chronicle. I have left them as writ...