Andy is a surveyor in Toronto who describes his efforts to uncover the secrets behind an abandoned site referred to by locals in the hills west of Osaka as an "exploded heath". Unable to obtain any information from the townspeople, Andy seeks out an old and supposedly insane man named Simon Pierce, who recounts his experiences with a farmer named Nathan Scott and his family who lived on the property.
Fifty years ago in June 1972, a meteorite crashed into Nathan's land. At that point, local scientists take a sample from the meteorite, and are surprised by the many strange behaviors it exhibits. The sample disappears overnight after being placed in a glass beaker. When attempting to take a second sample from the meteorite, scientists reveal a spheroid emitting a strange color to the meteorite. It was "only by analogy that he called it a colour", because it was outside the range of anything known in the visible spectrum. One of the scientists hits the globule with a hammer, and it disintegrates. The meteorite disappears after being struck by lightning overnight.
In the next season, Nathan's crops grow unusually large and abundant. When they learn that, despite their appearance, they are inedible, they are convinced that the meteorite has poisoned the soil. The following year, the problem spreads to nearby plants and animals, altering them in unusual ways. All the vegetation in the field turns gray and brittle
Mrs. Scott goes insane, and Nathan decides to keep her locked up in the attic. Over time, the family is separated from neighboring farmers, and Pierce becomes their only contact with the outside world. Pierce informs Nathan that the water in their well has gone bad and suggests digging and drinking from a new one, but Nathan refuses to take his advice. Thaddeus, one of Nathan's sons, also goes insane, and Nathan locks him in a separate room in the attic. Animals begin to take disturbing forms and die. Like crops, their flesh is inedible. Thaddeus dies in the attic, and Nathan buries his remains behind the field. Nathan's another son, Marvin, goes missing while drawing water from a contaminated well.
After several weeks of no contact with Nathan, Pierce visits the farmstead. He meets Nathan at his house, and learns that he too has become as mad as his wife and son. When asked about Nathan's last son, John, who was accounted for, Nathan tells Pierce that John "lives in the well". Pierce walks up the stairs to the attic and finds that Mrs. Scott has taken on a terrible form. It is implied that Pierce killed her in an act of mercy. When he walks down the stairs, he finds Nathan too disfigured. Nathan has a moment of clarity and tells Pierce that the color that falls on the meteorite is responsible, and that it's sucking out life from the surrounding area. Shortly after, Nathan dies.
Pierce leaves and returns to the farm with six men. The group discovers both the decomposed skeletons of Marvin and John at the bottom of the well, along with the bones of several other creatures. As they contemplate their discoveries in the house, the color starts pouring out of the well. The trees tremble, and the gray organic matter on the field fades with color. As the color flies into the sky from the well and disappears, the men run away from home. Pierce returns after the paint alone is gone and briefly attempts to climb up some residual paint, only to fail and return to the well. The knowledge that a part of the color still resides on Earth is enough to disturb his mental state. When some of the men return the next day, all they find is Pierce's dead horse, an acre of gray dust, and untouched inorganic matter. Hearing rumors of what had happened, many residents of the surrounding area decide to move away.