When Mariner IV radioed back the vision of Mars as a planet pocked with craters and unlikely to harbor life of any advanced sort, some newspapers wondered how science-fiction writers would take this. But, characteristic of their limitless imaginations, they always come up with an answer.

A. Bertram Chandler presents a particularly challenging response. If Mars is indeed barren, what are we to say of the wonderfully lifelike Mars worlds of H.G. Wells, Edgar Rice Burroughs. Otis Adelbert Kline, and so many others. They are too real to be lost! They must exist somewhere! And so Chandler sends his space expedition to that barren and lifeless Mars to find The Alternate Martians.

It's a science-fiction adventure, packed with action, and filled with some unexpected Red Planet surprises!