An Age
by Brian Aldiss
The story concerns Edward Bush, an artist searching for inspiration in the past.
When Bush returns from a long stay in the Jurassic, he finds that his nation (presumably the United Kingdom) has been taken over by a totalitarian government. He is immediately drafted into the military and given the mission to kill the scientist Silverstone (whom he had met as "Stein" in the past). As Bush mind travels again to fulfill his mission, he learns of Silverstone's new philosophical and scientific discoveries. Bush and Silverstone meet, travel to the Cryptozoic with a few allies, and decide together to usher in a new era of humanity, one enlightened by the realization that time flows backward. Bush returns to his present time, only to be imprisoned in a mental institution. Bush's father tries to see him but is prevented by doctors, who explain his son has had a breakdown brought on by excessive mind travel. Outside, a girl stands watching the hospital, presumably planning a rescue.