The tale tells of writer Michael Hayward who accidentally unleashes monstrosities from a forgotten age upon the Earth.
Hayward finds the formula for a narcotic drug in Ludvig Prinn’s De Vermis Mysteriis, creates the substance and begins taking it. It transpires that this drug is a "time drug" and it allows Hayward to read the akashic record and recover ancestral memories. Because he did not properly obey the instructions to use magical protections such as the Pnakotic pentagram, he exposed himself to the danger of the ‘the dwellers in the Hidden World’ who now took notice of him.
Hayward uses the drug to help him prepare a manuscript, which read:
|“||I dwelt in an archaic world. A world that had been long forgotten when Atlantis and Cimmeria flourished, a world so incredibly ancient that none of its records have ever come down through the ages.
The first human race dwelt in primal Mu, worshiping strange, forgotten gods—mountain-tall Cthulhu of the Watery Abyss, the Serpent Yig, Iod the Shining Hunter, Vorvadoss of the Gray Gulf of Yarnak.
And in those days there came to Earth certain beings form another dimension of space, inhuman, monstrous creatures which desired to wipe out all life from the planet. These beings planned to leave their own dying world to colonize Earth, building their titanic cities on this younger, more fruitful planet.
With their coming a tremendous conflict sprang into being, in which the gods friendly to mankind were arrayed against the hostile invaders. Foremost in that cyclopean battle, mightiest of Earth’s gods, was the Flaming One, Vorvadoss of Bel-Yarnak, and I, high priest of his cult, kindled
-there the manuscript ended.
The creatures from beyond, resembling gigantic eyeballs with small tentacles on their underside and a small puckered mouth, begin to mutate plants and animals surrounding his beachside house, and eventually even abduct one of his acquaintances, sending a misshapen wrecked undead version of the man back to Hayward, crawling along the beach. The entities then begin to directly impinge upon Earthly reality, the implication being they will mutate and overwhelm normal existence if not somehow stopped.
First published in the debut issue of Strange Stories in February 1939, "The Invaders" has since been reprinted several times, and has also been translated into Italian.