The Brain from Planet Arous

In this 1957 science fiction film, John Agar stars as Steve March, a young scientist whose body is possessed by an evil alien brain named Gor, threatening to destroy the world. Meanwhile, another alien brain named Vol inhabits the body of March's dog and waits for the perfect moment to strike. As Gor wreaks havoc on Earth, Vol's only hope is to find a way to escape the human body and exploit its vulnerability - the fissure of Rolando.