The year is 1895 and Pinky and the Brain are being kept in the laboratory of H.G. Wells. Brain builds a time machine because he wants to go back in time to keys moment in mouse evolution in order to change them and make mice the dominant form of life on Earth. When he returns to the present he hopes to be proclaimed the leader of the planet. Brain heads back in time and after a number of problems manages to teach mice how to make fire. When he returns to the present, he discovers that mice are the dominant form of life on the planet. Unfortunately, all the mice act like Pinky.