The Sign of Four (1890) was the second novel featuring Sherlock Holmes written by Sir Arthur Conan Doyle. Doyle wrote four novels and 56 stories starring Holmes, whom many regard as the best-known literary character ever invented.

The Sign of Four has a complex plot involving service in colonial India, a stolen treasure and a secret pact among four ex-convicts. It presents the detective's drug habit and humanizes him in a way that had not been done in the first novel, A Study in Scarlet; and introduces Doctor Watson's future wife, Mary Morstan. It is set in 1888.

The novel first appeared in the February 1890 edition of Lippincott's Monthly Magazine as The Sign of the Four, appearing in both London and Philadelphia. The British edition of the magazine originally sold for a shilling, and the American for 25 cents. Surviving copies are now worth several thousand dollars. Doyle was reputedly commissioned to write the story over a dinner with one of the magazine's agents, J.M. Stoddart, which was also attended by Oscar Wilde. At the dinner Wilde was also commissioned to write a novel, in his case The Picture of Dorian Gray.

The novel was published in book form in October 1890 by Spencer Blackett , this time as The Sign of Four; the title lacking the second the of the original. Different editions over years have varied between using one or other title and even some modern editions use the original five word title. As with the first story, A Study in Scarlet, produced two years previously, it was not particularly successful to start with. It was the short stories which were published from 1891 onwards in Strand Magazine which rapidly made Sherlock Holmes and his creator household names.

It has been filmed numerous times, both for motion pictures and television, the first time probably being in 1932 and starring Arthur Wonter and Ian Hunter .

External links

• Full text of The Sign of Four
• The Sign of the Four - in easy to read HTML format.

The Sign of Four is the title of an album by guitarists Derek Bailey and Pat Metheny