Dr. Charles Forbin (Eric Braeden) is the chief architect of Colossus, a new supercomputer designed to take over the nuclear weapons systems of the United States during the Cold War. But when the system is activated, it detects the existence of a counterpart in the Soviet Union and makes a request to be put in contact with this other machine. This triggers a series of events culminating in the two machines merging and demanding control of the world, while teams of scientists desperately try to stop it.