For centuries, interstellar prospectors had searched for the fabled worlds of the Three Kings, the lost El Dorado of the galaxy. But if any found it, they were never heard from again. The mad cyborg Prophet, Ishmael Hand, discovered the mysterious system, with artifacts indicating a superhuman technology, and he had refused to reveal its location before vanishing forever into history. Two more recent expeditions have found the Three Kings. A starfaring evangelist-Doctor Karl Woodward, preacher and leader of the starship The Mountain-followed a clue and found it, but never returned. Then a spacegoing salvage team followed Woodward's trail, and also vanished. Now a chance encounter between what's left of the once-mighty human military with an inexplicable alien force has brought an armed expedition to the third planet of the Three Kings, Kaspar. They will join forces with the survivors of the first two expeditions, who have been marooned both by alien powers and by human treachery, as they at last encounter the alien minds behind the mysterious triple planetary system-and they will face a decision that may determine the fate of the entire human race!