AllMovie

A pair of seemingly inert black crystalline rocks are actually intelligent extraterrestrial viruses planning the invasion and destruction of the Earth. Dr. Paul Cameron (Robert Culp) can hear their thoughts as they discuss their plans, a result of a metal plate in his head from a war injury that conducts their telepathic waves into his brain. He and his wife, Laurie (Salome Jens), believe that he is hallucinating. The aliens, however, target him for death, and will stop at nothing to kill him. Cameron, caught between feelings of paranoia and the fear that he is going insane, goes away for a rest with his wife, never realizing that they are now being stalked by their friend, Dr. Temple (Barry Atwater), his body and mind taken over by the aliens.