Dr. Brewer, an ex-botanist, has been acting strangely, spending nearly all his time in the basement of his house, working on his plant experiments. He had warned his children, Margaret and Casey, to stay out, but they sneak in and catch a glimpse of gigantic and very strange plants that almost seem life-like. They begin to worry even more when Margaret finds that her father has been eating plant food, sleeping on a layer of dirt, and bleeding green blood.