They came from the cold void. They whisper from the hills. They want your brain.

The story is presented as the testimony of Albert N. Wilmarth, a folklore professor at Miskatonic University, who becomes embroiled in a terrifying mystery after a series of disastrous, historic floods in rural Vermont. The floods wash up evidence of strange, non-human bodies in the rivers, reigniting local legends of malevolent, winged creatures in the hills.

Wilmarth is a skeptic, but he begins corresponding with Henry Akeley, a recluse living in an isolated farmhouse near the dreaded mountains. Akeley is a fervent believer in the legends and claims to have concrete, terrifying proof of the creatures' existence, a hostile, extraterrestrial race known as the Mi-Go. These entities, sometimes called the "Fungi from Yuggoth," are described as large, pinkish-black, crustacean-like creatures with multiple legs and antennae.

Akeley's letters grow increasingly urgent and fearful, detailing the Mi-Go's nefarious activities on Earth, mining precious minerals and, most chillingly, surgically removing human brains and preserving them in metal cylinders for interstellar travel. Akeley then abruptly invites Wilmarth to his farmhouse, claiming he has reconciled with the Mi-Go and possesses evidence that will shock him.

Wilmarth makes the journey and finds Akeley's house quiet. He meets the supposedly reconciled Akeley, who is now confined to a dark room and speaks in a low, monotonous whisper, presenting Wilmarth with a cylinder containing what he claims is his own preserved brain. The true, agonizing climax occurs when Wilmarth discovers that the "Akeley" he has been speaking to is not his friend at all, but a disguised Mi-Go, who was using the larynx of the real Akeley to talk.

The Whisperer in Darkness is a foundational novella of the Cthulhu Mythos and a masterwork of science fiction and horror. It codified the Mi-Go as a major threat and introduced the horrifying concept of brain transference, where a disembodied human brain is kept alive in a cylinder, condemned to travel the cosmos.