Brent is an American astronaut, part of a team sent to locate missing fellow American astronaut George Taylor. Following Taylor's known flight trajectory, the search-and-rescue team crash-lands on an unknown planet much like Earth in the year 3955, with Brent the only survivor of the team. What Brent initially does not know, much like Taylor didn't when he landed here before Brent, is that he has landed back on Earth in the future, in the vicinity of what was New York City. Brent finds evidence that Taylor has been on the planet. In Brent's search for Taylor, he finds that the planet is run by a barbaric race of English-speaking apes, whose mission is in part to annihilate the human race. Brent eventually locates some of those humans, who communicate telepathically and who live underground to prevent detection by the apes. These humans, who are in their own way as barbaric as the apes, want in turn to protect their species. Brent must figure out a way to save himself under the circumstances, which may be more difficult to accomplish in the battle between the dominant species on this planet.