"The Call of Cthulhu" is one of H. P. Lovecraft's best-known short stories.  It is the only story written by Lovecraft in which the extraterrestrial entity Cthulhu himself makes a major appearance.
It is written in a documentary style, with three independent narratives linked together by the device of a narrator discovering notes left by a deceased relative. The narrator pieces together the whole truth and disturbing significance of the information he possesses, illustrating the story's first line: "The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents. We live on a placid island of ignorance in the midst of black seas of infinity; and it was not meant that we should voyage far."