In the secluded hills west of Arkham lies a mysterious place known as the "blasted heath". The locals shun this place, withholding any information from outsiders. Curiosity gets the best of an unnamed surveyor from Boston, leading him to seek out an old man named Ammi Pierce for answers. Pierce shares a chilling tale of a farmer named Nahum Gardner and his family who once lived on the property.

It all started over fifty years ago when a meteorite crashed into Nahum's land in June 1882. Local scientists take a sample from the meteorite, only to witness baffling behaviors exhibited by the strange rock. The first sample disappears overnight, stored in a glass beaker. When a second sample is attempted, they discover a globule with a peculiar color that defies any known spectrum. Striking the globule with a hammer causes it to disintegrate, and overnight the meteorite vanishes after being struck by lightning.

The following season, Nahum's crops grow unnaturally large and abundant. However, they prove to be inedible, leading Nahum to believe that the meteorite has poisoned the soil. As time passes, the problem spreads, affecting the surrounding plants and animals, causing them to mutate in unusual ways. The once vibrant vegetation turns grey and brittle, a haunting sight.

Tragedy strikes the Gardner family as Mrs. Gardner succumbs to madness. Nahum takes the desperate measure of locking her away in the attic. The family becomes isolated, and Ammi Pierce becomes their sole connection to the outside world. Pierce alerts Nahum to the contaminated well water, urging him to dig a new well, but Nahum disregards the advice. One of Nahum's sons, Thaddeus, also falls victim to madness and is locked in a separate room in the attic. The livestock on the farm suffers a similar fate, their meat becoming inedible. Thaddeus dies in the attic, and his remains are buried behind the farm. Another son, Merwin, disappears while fetching water from the tainted well.

Weeks pass without any contact, prompting Pierce to visit the farmstead. He soon realizes that Nahum, too, has succumbed to madness. As Pierce questions Nahum about his missing son Zenas, Nahum cryptically reveals that Zenas "lives in the well". Disturbed by this revelation, Pierce ventures to the attic and is confronted by the horrifying form of Mrs. Gardner. In an act of mercy, Pierce ends her suffering. As he descends the stairs, he finds Nahum horribly deformed but still possessing moments of clarity. Nahum reveals that the color from the meteorite is to blame for the horrors that have befallen them, draining the life from the surrounding area. Shortly after this revelation, Nahum meets his end.

Determined to uncover the truth, Pierce returns to the farmstead with a group of six men. They make a gruesome discovery at the bottom of the well, finding the eroded skeletons of both Merwin and Zenas, along with other unfortunate creatures. Contemplating their findings, the color begins to pour out from the well, causing the trees to convulse and the once-grayed organic material to faintly glow. Fearing for their lives, the men flee as the color ascends into the sky and disappears. Pierce, however, witnesses a residual part of the color fail in its attempt to ascend and return to the well. This mere glimpse unsettles him, causing mental distress. When some of the men return the next day, all they find is Pierce's lifeless horse, acres of gray dust, and untouched inorganic matter. Word of the horrifying events spreads, compelling many residents of the surrounding area to abandon their homes and relocate.

"The Colour Out of Space" is a tale that delves into the unknown and the horrors that can be unleashed from something as innocuous as a fallen meteorite. Pierce's firsthand experiences with the gradual destruction wrought upon Nahum Gardner's farm paint a haunting portrait of a once-vibrant landscape consumed by an otherworldly color. The story serves as a cautionary tale, reminding us of the fragility of our environment and the potential consequences of tampering with forces beyond our understanding.