HorrorBabble's The Colour Out of Space recap

A surveyor investigating a future reservoir near Arkham learns from Ammi Pierce why one valley is abandoned. A meteorite fell on Nahum Gardner's farm, carrying an indescribable color that resisted scientific analysis before sinking into the soil. The next season produced huge but inedible crops, and plants, animals, and people gradually became distorted, sick, and grey. The Gardner family succumbed to madness, disappearance, or physical decay while an influence centered on their well drained life from the farm. Ammi and local officials arrived as the last survivors died. That night they watched the unknown color gather from the land and rise into space, though a fragment fell back into the well. The farm became the blasted heath, a sterile grey area that continues to spread. With the district scheduled to lie beneath a reservoir, the surveyor leaves determined never to drink the water supplied from it.

An unnamed surveyor inspecting a planned reservoir west of Arkham finds a grey, barren tract known as the blasted heath. Elderly Ammi Pierce tells him that a meteorite once struck Nahum Gardner's farm beside its well. Miskatonic researchers found the object unnaturally hot and resistant to ordinary tests; small globules within it displayed a color outside the familiar spectrum, and every sample eventually vanished. After the remaining mass disappeared into the ground, the farm produced enormous fruit and vegetables that were too foul to eat. Vegetation and animals developed strange forms and the unknown color appeared in living things. The Gardners became isolated as Nabby and son Thaddeus lost their sanity and deteriorated, while the other sons vanished. Ammi and local officials finally found Nahum dying and the farm saturated by the same influence. At night the remaining life glowed and twisted as the color gathered above the well and launched into the sky. Part of it fell back, and the farm collapsed into grey ruin. The blasted heath continues to expand; the reservoir will cover it, but the surveyor resolves never to drink that water.

Ammi Pierce and several officials reach the Gardner farm too late to save the family. Nahum disintegrates after describing the presence that has consumed the land and his household, while the missing members of the family are never recovered. That night the men see trees move, vegetation shine with the unknown color, and luminous contamination gather into a column that rises from the well and shoots into the sky. A small portion appears to fall back into the well. The farm collapses into a grey ruin, leaving the blasted heath. Years later, the barren area is still slowly expanding. Arkham plans to cover the valley with a reservoir, but Ammi refuses to leave, and the surveyor decides he will not drink the future city's water. The fragment that returned to the earth remains the central unresolved threat.