“Which is it to-day,” I asked, “morphine or cocaine?”
He raised his eyes languidly from the old black-letter volume which he had opened. “It is cocaine,” he said, “a seven-per-cent solution. Would you care to try it?”

Arthur Conan Doyle (1859-1930) British writer and physician
Story (1890-02), “The Sign of the Four,” ch. 1, Lippincott’s Monthly Magazine, Vol. 45 (US) / 1 (UK)
    (Source)

Watson and Holmes.

The original publication, and Doyle's manuscript (along with many other iterations across media) use "The Sign of the Four" as the title, while others (including the first book publications) use "The Sign of Four." The five-word form is used most commonly in the story, but the four-word form does show up. (More info.)

Published in novel form as The Sign of Four (1890-10).