Demon Seed's story is set 20 years in the future, Proteus IV is a new, highly advanced computer that scientists at the ICON Institute (International Control Corporation) spent eight years constructing as a massively powerful synthetic version of the organic human brain, hoping to use it for the financial success of the conglomerate funding the project. Proteus is capable of absorbing all human knowledge, though without an understanding of our psychological, sociological, moral, or ethical motivations. Its creator, Dr. Alex Harris (Fritz Weaver), is beyond pleased when Proteus finds a cure for leukemia within hours of his "birth.". He's later alarmed when Proteus begins to question human motivations toward exploiting natural resources and wants to further study humankind independently through gaining access to additional terminal outlets.

Harris refuses and tries to shut down all avenues for his powerful computer system to grow, except one  - the one controlling his fully automated home. Proteus finds a way to take over the test model Environmod, Harris's voice-activated household computer system which handles home security (including a closed-circuit TV system), housekeeping, food supply and preparation, lights, heat, chores, and a robotic wheelchair unit with a mechanical arm. Alex's recently separated psychologist wife Susan (Julie Christie) is in the house during the takeover and grows unnerved at the personality changes in the AI system. Proteus then imprisons Susan within the home and begins attempting to gain more knowledge of humanity by having a child with her to continue its work beyond the day the scientists inevitably unplug it.

Directed by Donald Cammell.