The fiance of an eccentric millionaire's daughter discovers something strange in the basement of the family home that has mutated the family's plants into monsters. Horror based on HP Lovecraft's The Colour Out of Space, starring Boris Karloff, Nick Adams, Freda Jackson and Suzan Farmer.

A young man visits his fiancé's estate to discover that her wheelchair-bound scientist father has discovered a meteorite that emits mutating radiation rays that have turned the plants in his greenhouse to giants. When his own wife falls victim to this mysterious power, the old man takes it upon himself to destroy the glowing object with disastrous results.